This Editorial Guide is used for Education Purposes Only. It is used in the Authoring Courses and Certifications. It is based on the January 2026 Editorial Guide.

Respiratory tract

321667001 |Respiratory tract structure (body structure)|. In SNOMED CT, respiratory tract has the same meaning as the Nomina Anatomica term apparatus respiratorius , which includes the structures through which air passes from the nares to the alveoli. The oral cavity is not included. In common usage, respiratory system may have the same meaning as respiratory tract ; but not in SNOMED CT. Respiratory system does not mean the global respiratory system that might include the CNS components of breathing. Pleura are part of the lower respiratory system, but not a part of the lower respiratory tract.

Upper aerodigestive tract

This phrase has several meanings. The SNOMED CT concepts 119253004 |Upper aerodigestive tract structure (body structure)| and 361922007 |Entire upper aerodigestive tract (body structure)| have the meaning based on the following reference: Cancers of the upper aerodigestive tract constitute approximately 4% of all malignancies. These include cancer of the lip, tongue, major salivary glands, gums and adjacent oral cavity tissues, floor of the mouth, tonsils, oropharynx, nasopharynx, hypopharynx and other oral regions, nasal cavity, accessory sinuses, middle ear, and larynx (Upper aerodigestive tract cancers, Cancer 1995 Jan 1;75 (1 Suppl): 147-53). This definition matches the tumors included in the CAP Cancer Checklist for upper aerodigestive tumors. The esophagus, or at least the cervical esophagus, may be included, but not in SNOMED CT .

58675001 |Upper respiratory tract structure (body structure)| includes the nasal cavity, paranasal sinuses, nasopharynx, oropharynx, and larynx

82094008 |Lower respiratory tract structure (body structure)| includes the tracheobronchial tree (from the trachea through the terminal bronchioles) and the lungs, including the alveolar respiratory tract (which extends from the respiratory bronchioles to the alveoli).

400141005 |Lower respiratory system structure (body structure)| includes the lower respiratory tract and the pleura.

The interarytenoid fold forms part of the inlet of the larynx. The fold has two surfaces, one forming part of the wall of the supraglottic larynx, the other forming part of the wall of the hypopharynx (the food tube behind the larynx, leading to the esophagus). The 102295003 |Structure of hypopharyngeal aspect of interarytenoid fold (body structure)| may be considered part of the hypopharynx, the larynx, or both. A tumor of this site is categorized as a tumor of the hypopharynx, and not the larynx, but the 105585004 |Interarytenoid fold structure (body structure)| is considered part of the larynx.

SNOMED CT does not give a Part of relationship between the hypopharyngeal aspect of the interarytenoid fold and the interarytenoid fold. This emphasizes SNOMED CT modeling based on the relationship of anatomical entities and disorders and procedures and not simply by reading term names.

SNOMED CT differentiates between the bone underlying the nasal turbinates and the actual turbinates:

Bones underlying the turbinates,

• 118648008 |Inferior nasal turbinate bone structure (body structure)|

• 122491002 |Middle nasal turbinate bone structure (body structure)|

• 122492009 |Superior nasal turbinate bone structure (body structure)|

Turbinates, which include bone, overlying mucous membranes, and other tissue,

• 6553002 |Inferior nasal turbinate structure (body structure)|

• 122491002 |Middle nasal turbinate bone structure (body structure)|

• 65289004 |Superior nasal turbinate structure (body structure)|

The 118648008 |Inferior nasal turbinate bone structure (body structure)| is a facial bone and skull bone. And, parts of the ethmoid bone form the middle, superior, and supreme nasal conchae. This means that the bones of the middle, superior, and supreme turbinates are not bone organs.

This Editorial Guide is used for Education Purposes Only. It is used in the Authoring Courses and Certifications. It is based on the January 2026 Editorial Guide.

SNOMED CT uses the Foundation Model of Anatomy (FMA) definition of body part and body part subdivision for some concepts. For example, the joint regions discussed below are classified as body part subdivisions, since that is what is intended by the diseases and procedures that use these terms in their definitions. They are not body parts because they are defined, not by a set of bones, but rather by a particular joint and its surrounding structures. However, our interpretation of the word region is based on common usage and is intended as a three-dimensional structure, not the FMA two-dimensional definition of body region. In other words, these regions are not simply surface regions (skin), but also include the three dimensional underlying structures (subcutaneous tissues, bones, muscles, tendons, fascia, vessels and etc.).

Surface regions

Many concepts contain the phrase surface region. These could be interpreted as massless (immaterial) mathematical surfaces, but a clinical terminology would have no direct use for such meanings in clinical records. They could be interpreted as having mass (not immaterial), but the depth then is arbitrary. Should it be just skin deep, or should it include deeper layers of the surface? If only skin deep, the meaning of these concepts would overlap with concepts for skin regions. If deeper, the meaning would possibly be the same as the generic structure concepts.

The named regions of the abdomen are by tradition divided horizontally by the transpyloric plane and the interspinous plane, and vertically by the midclavicular plane. The lateral regions are therefore bounded above by a plane that is inferior to the ribs. In contrast, the flank is the lateral region of the abdomen bounded above by the ribs. Thus some parts of the hypochondriac regions, which are superior to the transpyloric plane but inferior to the ribs, would be considered also part of the flank. The hypogastric region is also sometimes called the pubic region.

The term abdominal cavity has two meanings, one including the pelvic cavity , the other excluding it. Abdominal cavity structure includes both. Abdominal cavity proper excludes the pelvic cavity.

The FMA definition of body organ is also used. Organs include individual bones, joints, muscles, arteries, veins, lymph vessels, nerves, and etc. Concepts that include groups of organs are frequently used in SNOMED CT. In most cases, these have been part of the subsumption hierarchy (IS A hierarchy) of the particular organ type, that is, they are kinds of organs.

For concepts that refer to the collection of organs (rather than organs in a collection), there is another concept that is a, kind of, organ system subdivision. Many such collections do not yet have corresponding organ system subdivision concepts. The default is to interpret concepts as denoting organs, rather than organ system subdivisions.

In general, organs are made up of tissue, and tissue is made up of cells. However, a cell is not necessarily part of tissue, and tissue is not necessarily part of a named organ.

Arteries, veins, nerves, and the bronchi form tree-like structures that distribute across multiple regions. Because of their size and links with other structures, they require slightly different modeling. FMA divides tree structured organs as: organs with organ cavities and organs that are solid.

Organ with organ cavity has a subtype, hollow tree organ. The hollow tree organs are:

• Tracheobronchial

• Biliary

• Vascular

Among the solid organs, there is one category, neural , that is tree-structured (see: Nervous system; neural tree).

Male and female are unnecessary descriptions in describing the breast. Gender information should be obtained and recorded separately in the information model. New content that requests male or female breast will not be accepted so as not to duplicate gender-specific anatomical concepts.

This Editorial Guide is used for Education Purposes Only. It is used in the Authoring Courses and Certifications. It is based on the January 2026 Editorial Guide.

There are processes for making decisions about adding or changing content in SNOMED CT.

Change requests

All change requests, whether for new content or for change to existing content, go through a request submission approval process. It involves review by authors to determine that there is:

• International applicability

• Compliance with Understandable, Reproducible, Useful (URU) principles

• No duplication with existing content

• No link to existing larger projects, as detailed in a Content Tracker document

• No conflict with existing collaboration agreements (e.g. Logical Observation Identifiers Names and Codes (LOINC) agreement)

Requests that are rejected may be appealed by the submitter.

Requests may be deferred for a number of reasons including questions about:

• How to model the concept; which attributes may be used

• Concept meaning

• Literature reference missing or inadequate

• Use case unclear

Resolution of deferrals may result in a decision delay requiring:

• A larger project or work item or

• Referral, internally, to other groups for decision. This depends on the complexity of the request and understanding of the wider impact.

Results of adjudication are received by email from the Content Request System (CRS). Simpler issues can be resolved expeditiously (e.g. by a ruling from the Chief Terminologist).

This Editorial Guide is used for Education Purposes Only. It is used in the Authoring Courses and Certifications. It is based on the January 2026 Editorial Guide.

Death is an event, not a disorder.

Sudden cardiac death

Sudden cardiac death is a term used in clinical practice. It refers to an arrhythmia that results in sudden loss of cardiac function which, if not quickly reversed, will lead to actual death. The FSN Sudden cardiac death (disorder) is modeled as a subtype of 127337006 |Acute heart disease (disorder)|. It should not be classified as death. Individuals with sudden cardiac death have not necessarily been declared dead and are frequently revived. It is regarded as a subtype of cardiac dysrhythmia.

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When considering the creation of a new morphological abnormality concept, consider the following:

• When the name of a potentially new morphology is the same as the disease, creation of that new morphologic abnormality concept may not be beneficial since it would not be very morphologically descriptive.

• Determine if there is benefit in creating a new morphology for a very small number of rarely used leaf nodes. If the new morphology is needed to differentiate two non-leaf concepts, that would be sufficient to create the new morphology. Otherwise, use the nearest existing morphologic abnormality.

This Editorial Guide is used for Education Purposes Only. It is used in the Authoring Courses and Certifications. It is based on the January 2026 Editorial Guide.

A preferred term (PT) is the description that is deemed to be the most clinically appropriate way of expressing a concept in a clinical record. It represents a common word or phrase used by clinicians to name a concept in clinical practice or in the literature. It is the synonym that is preferred in a language or dialect.

The use of a description can vary between different languages, dialects and contexts. A description may be preferred in some dialects, acceptable in others, and may not be used in some dialects. A Language Reference Set is used to specify the descriptions that are preferred or acceptable in each language or dialect.

A concept may have two descriptions marked as PT, one for each language.

For example, 32849002 | Esophageal structure (body structure)| has

• PT: Esophageal structure (US)

• PT: Oesophageal structure (GB)

A PT for one concept may also be a synonym for another concept.

For example,

• 84162001 | Cold sensation quality (qualifier value)| has a preferred term of cold

• 82272006 | Common cold (disorder)| also has a synonym of cold

In both concepts, cold represents a common clinical phrase used to capture the meaning of the concept.

The PT is indicated by the acceptabilityId field, for a particular language or dialect.

This Editorial Guide is used for Education Purposes Only. It is used in the Authoring Courses and Certifications. It is based on the January 2026 Editorial Guide.

A disorder is always and necessarily an abnormal clinical state.

Disorder modeling information is as follows:

• Specific Clinical finding and Disorder Modeling

This Editorial Guide is used for Education Purposes Only. It is used in the Authoring Courses and Certifications. It is based on the January 2026 Editorial Guide.

A concept has multiple associated descriptions.

Each description has a description type and a unique numeric description identifier.

• Fully specified name (FSN) and synonym (SYN) are description types in SNOMED CT.

This Editorial Guide is used for Education Purposes Only. It is used in the Authoring Courses and Certifications. It is based on the January 2026 Editorial Guide.

The following figure shows the structure of genetic, developmental, and congenital categories, along with non-genetic, non-developmental, and postnatal categories. A dimension, called extrinsic physical force , is included to distinguish deformations from malformations. The sections of the diagram represent categories formed from the combination of the dimensions, each which represents the answer to one of the following questions:

• Is it genetic or not?

This Editorial Guide is used for Education Purposes Only. It is used in the Authoring Courses and Certifications. It is based on the January 2026 Editorial Guide.

Fractures should be agnostic as to whether they are pathologic or not, unless specified in the FSN or could only be caused by trauma (e.g. open fractures). Although most fractures are traumatic, there are some pathological fractures. Based on its FSN and text definition, if the word pathological is present, use Pathologic fracture (morphologic abnormality).

This Editorial Guide is used for Education Purposes Only. It is used in the Authoring Courses and Certifications. It is based on the January 2026 Editorial Guide.

This section considers scope as it relates to the incorporation of proprietary names (e.g. brand names of drugs, devices, clinical forms or tools) into SNOMED CT.

Brand name of drugs and devices

Proprietary names are the names that have been assigned to products, usually drugs and devices, by their corporate producers. They do not require a license from the producer. It is both necessary and useful to include proprietary names in a health terminology. SNOMED International does not need to obtain the permission of the trademark owner simply to include a reference to the brand name drug in SNOMED CT. However, they should not be included in the International Release but instead in National Extensions. This is because proprietary names may refer to different products depending on the country and the meaning of these names are dependent on the country or jurisdiction in which the product is approved.

Exception

An exception to the inclusion of brand names of devices has been made to include a select number of devices used in glaucoma treatment. The Eye Care Clinical Reference Group agreed on the list of these devices, acknowledging their consistent international use and representation. The exception is necessary due to the challenge of describing these devices clearly and unambiguously in the SNOMED FSN. Since the selection of these devices is based on their brand names, it is essential to include them in SNOMED CT.

The owner of a form or tool may be an individual or organization that created it; the healthcare organization that employed the individual; or it may be a commercial organization to which the rights were assigned.

Incorporating the name of a clinical form or tool (e.g. the XYZ Test (staging scale)), or the name of the score generated by a form or tool (e.g. the XYZ Test Score (observable entity)) into SNOMED CT does not require a license from the owner. Reference to the owner of a clinical form or tool loosely refers to the person or organization that owns the intellectual property rights of the form or tool. This may be the individual or group that originally created the form or tool, the organization that employed the creators, or a commercial organization to whom the creators assigned their intellectual property rights. It is possible that the owner holds a trademark (which may be registered or unregistered) representing the name or score, but simply incorporating that word into SNOMED CT does not infringe on the trademark.

A concept may be introduced into SNOMED CT that represents the text of questions, answers, or scores. For example, a form may include a question about a person's ability to dress and a range of possible answers. SNOMED CT may incorporate neither the text of the question nor any of the possible answers, but instead may incorporate a concept such as ability to dress. Similarly, if the form contains 20 questions, SNOMED CT may want introduce 20 concepts, for XYZTest_Result1 , XYZTest_Result2, etc. to XYZTest_Result20.

The incorporation of a single concept into SNOMED CT , based on a question, answer, or score on a clinical form is highly unlikely to infringe on the copyright. However, if SNOMED CT systematically introduces a concept for every single question on a clinical form, it is likely to infringe on the copyright.

These concepts (e.g. ability to dress) may already exist in SNOMED CT, or they may be added in other contexts (This does not apply to concepts that represent specific questions within a form). This is unlikely to result in a copyright infringement.

Questions

A clinical form or tool, including the wording of the individual questions within the form or tool, is generally a literary work and qualifies for copyright protection (except in the case of the simplest of forms). The copying of all or any substantial part of a literary work, without a license from the owner, infringes on the copyright.

Answers

Certain questions may have a range of pre-determined answers. This could be as simple as Yes/No or a number within a specific range, but may also be more substantial (e.g. needs help cutting, spreading butter, etc. , or requires modified diet). Incorporating very simple answers into SNOMED CT does not require permission. However, incorporating more substantial textual answers into SNOMED CT generally infringes on the copyright. This usually does not apply to individual answers, but it almost always applies when entire sets of answers are incorporated.

Scores

The principles that apply to individual answers also apply to the overall score generated by a clinical form or tool. The incorporation of numbers does not infringe on the copyright. However, when each possible score has an associated textual description and all possible scores and descriptions are incorporated into SNOMED CT, a license is required.

• For example,

  • 443807003 | EuroQoL five dimension questionnaire (assessment scale)| is a SNOMED CT concept. However, these scores are subject to copyright protection, therefore cannot be added to SNOMED CT:

    • EuroQol Five Dimension (youth) doing usual activities score

This Editorial Guide is used for Education Purposes Only. It is used in the Authoring Courses and Certifications. It is based on the January 2026 Editorial Guide.

Patient vs Subject

The |Situation with explicit context (situation)| hierarchy is intended for concepts that explicitly include contextual information. Context can include whom the finding is about, or on whom a procedure is performed. These concepts can be used to represent different meanings, e.g., past history, family history, planned care, excluded diagnosis, etc.

In contrast, a concept in the Clinical Finding or Procedure hierarchy has a default Intended Use of the subject of the record. This context can be overridden by the information model.

• For example,

  • The concept |Asthma (disorder)| could be used in a family history field to represent a family history of asthma.

However, including the term subject or patient within a Clinical finding or Procedure concept prevents that concept’s context from being overridden by the information model.

• For example,

  • The concept |Patient immunocompromised (finding)| could not be used in a family history field to represent that a family member is immunocompromised.

Therefore, the use of patient and subject should be used only when necessary.

Descriptions should use the word subject, not patient, if required, as subject is broader than patient.

• For example,

Subject refers to the subject of record, who may, in some circumstances, not be the patient.

Best practice is to create a contextless concept.

• Example - finding,

  • Patient unable to chew with denture (finding) - incorrect

    • Unable to chew with denture (finding) - correct

Descriptions with caregiver should be as follows:

• An FSN should use caregiver as (one word).

• There should be a synonym using carer.

For example,

• Synonym: Carer able to cope

This Editorial Guide is used for Education Purposes Only. It is used in the Authoring Courses and Certifications. It is based on the January 2026 Editorial Guide.

Germline chromosomal abnormality co-occurring and causing disorder: 41040004 | Complete trisomy 21 syndrome (disorder)|

If the phenotype is always caused by a specific genotype, there is no need to include the cause in the FSN or clarify with a Due to relationship.

Germline nucleotide sequence variant co-occurring and causing disorder: 190905008 | Cystic fibrosis (disorder)|

Modeling for germline mutations causing conditions, such as cystic fibrosis, should have mutations, Occurrence = congenital, and Due to (attribute) the mutation finding.

For example,

• Cystic fibrosis due to G542X mutation

Somatic mutations leading to cancer, such as malignant melanoma with BRAF V600E mutation , should have dual supertypes , including the malignant disorder and the somatic mutation, and Due to (attribute) with the associated somatic mutation finding.

For example,

• Melanoma with BRAF V600E mutation

Representing two associated findings in a single concept may be convenient for recording; however, the representation of the two notions should be recorded separately.

For example,

• Breast cancer occurring with positive estrogen-receptor assay should be recorded in the information model as two separate concepts

This Editorial Guide is used for Education Purposes Only. It is used in the Authoring Courses and Certifications. It is based on the January 2026 Editorial Guide.

The 123037004 |Body structure (body structure)| subhierarchy includes both anatomical structures and morphologic abnormalities

This Editorial Guide is used for Education Purposes Only. It is used in the Authoring Courses and Certifications. It is based on the January 2026 Editorial Guide.

The Structure-Entire-Part (SEP) model

SNOMED CT uses a structure-entire-part triple, known as the SEP triple , to represent anatomical structures. The following Relationships provided a way for the anatomy in CTV3 to be mapped to RT:

The SNOMED CT anatomy hierarchy differentiates classes of entire anatomical entities from classes of parts of entire anatomical entities.

Entire concept : Denotes a class that is instantiated by entire anatomical entities of some kind: entire heart is instantiated by all individual hearts.

Entity Part concept: Denotes a class that is instantiated by all anatomical entities that are a proper part of some entity of a given kind: heart part is instantiated by all entities that are a proper part of some heart, e.g. my mitral valve, your right ventricle, Joe's sinus node. Heart part is not instantiated by any heart.

Entity Structure concept : Subsumes both the related Entire and Part concepts. Consequently, it denotes a class which is instantiated by anything that instantiates either the Entire or the Part. For instance, Heart structure is instantiated by my heart, my mitral valve, your heart, your right ventricle, Joe's sinus node, Joe's heart, etc.

The code named Liver structure in CTV3 is equivalent to Liver structure in the diagram above. Both the CTV3 code for Liver structure and the SNOMED RT code for Liver are interpreted to mean Some or all of the liver. Site attributes (PROCEDURE SITE, FINDING SITE) will usually take the value liver structure rather than entire liver , since typically the site of a liver disorder or procedure on the liver is not necessarily the entire liver.

Adding the Entity Structure codes is a convenience to assist with the logic-based aggregation of references to the entity or its parts. The implication of this view is that the E of the SEP triple is the code that should be regarded as the one that represents the real anatomical entity that is named.

• For example, the code for entire liver is the one that should correspond to the code for liver in the Foundational Model of Anatomy (FMA). The subtype hierarchy __ for entire liver fits much better with the FMA hierarchies, and indeed it might be possible to completely reconcile SNOMED’s non-Structure components with FMA anatomy.

A database has been developed that categorizes codes in the physical anatomical entity hierarchy according to their status as S structure, P Part or E Entire, and provides the corresponding S and P code for each E code. This should provide some value to implementers. It can help with navigation, coordination with formal ontologies of anatomy, and selection of codes for postcoordination.

Where there were two concepts with the same name, the SNOMED RT code was to become the S code, and the CTV3 code was to become the E code. There are still instances of unrecognized pairing of the RT-CTV3 S-E pair, where neither codes FSN has been changed according to the naming conventions in this document. When these unmatched pairs are identified, it is our practice to change the FSNs accordingly, and to make the E code have a subtype IS-A link to the S code.

Some S codes do not currently have a corresponding E code subtype, and there was no policy that required that such E codes be created during the merger of SNOMED RT and CTV3. However, it is likely that such a policy will be enforced in the future.

The SEP triple may give the impression that all S codes have exactly two children, one E and one P , with all of the remaining descendants placed under P. Again, in the past this degree of modeling consistency was not always followed. Some codes were purposely made subtypes of the S that are not strictly part of the corresponding E.

• For example, perirenal tissue is a kidney structure but not a part of the kidney. It is used to define perirenal abscess so that it is subsumed by renal abscess. While a perirenal abscess is not strictly within the substance of the kidney, it is still considered a kind of renal abscess, and the S anatomy hierarchy is used to support this inference.

This policy has introduced undesirable variation and arbitrariness into the terminology, and future revisions will seek to eliminate these variations. Where a code is needed for a site that is really meant to extend to entities that are not part of any kidney, this will be made clear in the name, e.g. Structure of kidney and perirenal tissue.

The E code needs to be interpreted with care when the x name refers to entities that do not have the property of identity, meaning that they are not countable wholes, or could be interpreted as non-countable. In this circumstance, the interpretation of E means some portion of the thing being named.

• For example, tissue and types of tissue such as fascia, muscle, tendon, bone tissue, connective tissue, skin, mucosa/mucous membrane, nerve tissue, etc. Muscle, tendon, bone and skin can identify a type of tissue as well as an individual organ of that type. Bone tissue has no identity, but a particular bone does have identity.

To use skin as the archetypal example, the E code for skin of finger means a portion of the skin of a finger, so all of its subtypes must also be portions of skin. The S code for skin of finger then has a subtype P which would mean proper part of a portion of skin of finger. This admits subtypes that are not kinds of skin, but may be parts of skin, including layers, e.g. epidermis of finger (meaning a portion of epidermis of finger) could be a proper part of a portion of skin of finger.

We regard the E code for x tissue, x layer to have the meaning portion of X tissue , and therefore regional subdivisions of tissue types are direct subtypes.

• For example, transitional epithelium of urinary tract, as an E kind of code, should be a supertype of transitional epithelium of urinary bladder. The reason is that (portion of) transitional epithelium of urinary bladder is a kind of (portion of) transitional epithelium of urinary tract.

We also deal with layers the same way.

• For example, we regard serosal layer and serosa tissue as meaning the same thing, since all serosal tissue is conifigured as a layer, and it can’t be a serosa without being a layer; and their E codes mean portion of serosal layer or portion of serosal tissue.

• As another example, layer of retina would be a supertype of nerve fiber layer of retina, and also a supertype of retinal epithelium, where retinal epithelium represents a portion of the epithelium of the retina and is therefore a kind of (portion of) a layer.

The identity/countability issue extends to a problem differentiating groups of entities from one of the group.

• For example, consider x = lymph node group , y = lymph node. In this case, the group should be linked to the member via an appropriate Relationship(not yet in SNOMED CT), such as has-member. In those cases where y is always necessarily a member of group x, it could be linked via a member-of Relationship(also not yet in SNOMED CT).

What does part of mean?

There are several possible ways of interpreting part of. In SNOMED CT, A part of B means that in normal anatomy, the entire structure A is structurally included in B. Another way of saying it is that A is part of B if there is no part of A that is not also part of B.

• For example, the humerus is not part of the shoulder region, because the distal humerus is part of the humerus, and the distal humerus is not part of the shoulder region.

We do not use part of for non-anatomical meanings, such as grouping tests together in batteries, nor do we use it to indicate Relationships that are not strict anatomical inclusion.

Some recent work has begun to differentiate between part of that is reflexive (that is, an entity is in some sense a part of itself , much the same that a set can be viewed as a subset of itself), versus proper part of , where an entity cannot be a proper part of itself. For now, we regard part of Relationships as implying strict partonomy.

There is sometimes confusion about parthood as opposed to location.

• For example, an embryo is not part of a mother's body, but a kidney is. The anatomy section is composed mainly of canonical parts; but a few abnormal parts are included to permit them to be used as the location of tumors or injuries.

• For example, a Meckels diverticulum is a body structure that is part of the small intestine, and it is also a morphological abnormality. Likewise some stomas and other post-surgical structures are considered part of the body. A transplanted liver or kidney would be considered part of the body, as a post-surgical structure, even though the transplanted organ is not genetically identical. Likewise transplanted bone marrow is part of the body.

Non-living implants and devices, and foreign bodies, on the other hand, are considered to be located in the body, but not part of the body.

For more information on part of relationships in the anatomy concept model, please see .

The currently distributed part of Relationships need to be much more extensively modeled and quality assured. At present they are not defining , that is, their Characteristic Type in the relationship file is additional, and, therefore, they do not affect the classifier behavior. A substantial amount of effort has gone into a draft of the updated part of Relationships; these will require review and approval before incorporation into the release. This will eventually result in the SEP triplet structures and part of relations being strictly paralleled. It is a matter of time to implement and quality assure the changes.

The SEP structure, combined with the inference mechanism that is used with SNOMED CT, allows us to take advantage of anatomical Relationships to infer subsumption, IS_A Relationships between disorders, procedures, and other entities without reference to part of Relationships. The SEP structure also permits us to sufficiently define anatomical structures without reference to part of Relationships (making them necessarily true , but not among the necessary and sufficient conditions).

• For example, the Structure of left hand can be sufficiently defined as a hand structure with laterality = left. This definition is sufficient. Converting the part of Relationships to have Characteristic Status = defining will require significant changes to the current model.

Points, lines, and surfaces can be considered to be massless. The FMA calls these immaterial. It is important to differentiate the codes/names for these entities from those that are intended to represent entities that have mass. At present, the concepts under anatomical spatial entity represent massless entities. Massless entities are not represented using the SEP model. It is conceivable that users may want to reference parts of a surface, and to enable this we would need to apply the SEP model to anatomical spatial entities, or else adopt defining part of Relationships.

This attribute provides information on whether a body structure is left, right, or bilateral. It is applied only to bilaterally symmetrical body structures which exist on opposite sides of the body.

With the addition of lateralized content in the International Release, the need for unspecified unilateral concepts is removed, as well as potentially dangerous, if used directly in a patient record. Unilateral concepts will not be accepted.

This Editorial Guide is used for Education Purposes Only. It is used in the Authoring Courses and Certifications. It is based on the January 2026 Editorial Guide.

The endocrine system is composed of the endocrine pancreas, pineal body, paraganglia, paraaortic bodies, parathyroid glands, endocrine ovaries, endocrine testes, adrenal glands, pituitary gland, thyroid gland, juxtaglomerular apparatus of the kidneys, and some diffuse neuroendocrine structures. Certain parts of the thymus produce endocrine hormones, but the thymus itself is not part of the endocrine system.

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This Editorial Guide is used for Education Purposes Only. It is used in the Authoring Courses and Certifications. It is based on the January 2026 Editorial Guide.

Action verbs should be written in noun form within SNOMED CT descriptions. This most often means the root form of the verb will end with a suffix of –tion, -sion, -ment, -al, -ence, or -ance.

• For example,

  • Destruction instead of destroy

  • Incision instead of incise

  • Replacement instead of replace

  • Removal instead of remove

  • Maintenance instead of maintain

However, the root form of the verb may be used when it does not make a word when ending in noun suffixes.

• For example,

  • Control

  • Release

Lastly, the verb with a suffix of –ing may be used when the root form of the verb may cause ambiguity in the meaning, i.e., the root form of the verb could also be a physical object.

• For example,

  • Wiring instead of wire

  • Suturing instead of suture

Exceptions,

Common usage may dictate some exceptions.

• For example,

  • Repair instead of repairment

Although ‘repairment’ may be considered a valid word, its use has fallen out of common usage in comparison to ‘repair’.

A past tense verbal phrase should not be used to name a procedure, since it indicates that the procedure was done in the past.

• Unacceptable example,

  • Hand tendon ganglion excised indicates the procedure was done, as a past tense declarative statement.

• However, the following is an acceptable example using a noun phrase.

This Editorial Guide is used for Education Purposes Only. It is used in the Authoring Courses and Certifications. It is based on the January 2026 Editorial Guide.

Disorders which involve congenital anomalies are defined with:

• Occurrence (attribute) = Congenital (qualifier value)

• Associated morphology (attribute) = Morphologically abnormal structure (morphologic abnormality)

• Pathological process (attribute) = Pathological development process (qualifier value)

Therefore, congenital does not need to be represented as the Associated morphology (attribute) target value. Congenital anomaly morphology concepts usually have non-congenital parents.

This Editorial Guide is used for Education Purposes Only. It is used in the Authoring Courses and Certifications. It is based on the January 2026 Editorial Guide.

This Editorial Guide is used for Education Purposes Only. It is used in the Authoring Courses and Certifications. It is based on the January 2026 Editorial Guide.

SNOMED CT is arranged as a polyhierarchy. A hierarchy is defined as an ordered organization of concept codes linked together through IS A relationships. Concept codes are linked to their more general parent concept codes directly above them in a hierarchy. Concepts with more general meanings are usually located at the top of the hierarchy and then at each level down the hierarchy the meanings become increasingly more specialized.

For general modeling information, use the following links to jump to the following pages:

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The morphologic abnormality subhierarchy is located two levels below the Body structure hierarchy with siblings Apoptosis and Structure resulting from tissue repair process:

• SNOMED CT concept

  • Body structure (body structure)

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Concepts from the Morphologic Abnormality hierarchy should not be used in place of concepts from the Clinical Findings hierarchy, even though they appear to refer to similar clinical situations.

• For example

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The ear includes the external, middle and inner ear. The external ear has two main parts, the auricle (also called the pinna) and the 84301002 |External auditory canal structure (body structure)|.

The external auditory canal has the synonym external auditory meatus. The external auditory meatus is not just the external opening of the canal, but rather the canal extending to the ear drum ( 42859004 |Tympanic membrane structure (body structure)|).

The 61671002 |Structure of internal acoustic meatus of temporal bone (body structure)| (SYN, internal auditory canal, is not part of the ear. As described in the FSN, it is an opening in the temporal bone, and is primarily a nerve conduit that anatomically parallel to the external auditory canal.

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In addition to the guidance found here in the Editorial Guide, please see information on the use of templates at SNOMED CT Templates.

Templates are created by authors in an attempt to standardize the modeling, naming, case significance, etc. of certain subhierarchies of the terminology, though it is recognized that not every concept may conform to a prescribed pattern. The modeling approach may be difficult to apply in all cases, but domain-specific templates are being developed to ensure modeling consistency and accuracy.

When to create a template

No template is necessary if less than 50 concepts are affected. In cases of small numbers, check if existing templates can be generalized and/or look to add elements as optional rather than mandatory.

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This Editorial Guide is used for Education Purposes Only. It is used in the Authoring Courses and Certifications. It is based on the January 2026 Editorial Guide.

SNOMED CT is arranged as a polyhierarchy. A hierarchy is defined as an ordered organization of concept codes linked together through IS A relationships. Concept codes are linked to their more general parent concept codes directly above them in a hierarchy. Concepts with more general meanings are usually located at the top of the hierarchy and then at each level down the hierarchy the meanings become increasingly more specialized.

Selected SNOMED CT attributes have a hierarchical relationship to one another known as attribute hierarchies. In an attribute hierarchy, one general attribute is the parent of one or more specific subtypes of that attribute. Concepts defined using the more general attribute can inherit concepts modeled with the more specialized subtypes of that attribute.

Domains

The following are the 19 domains arranged in alphabetical order.

• Environment or geographical location (environment / location)

• Organism (organism)

• Physical force (physical force)

• Qualifier value (qualifier value)

The pages that follow contain tables that are generated from the Machine Readable Concept Model (MRCM). The tables contain Attribute Summaries for those domains with attributes, information on Group(ed), Cardinality, and In-group cardinality, and Range constraints. The MRCM tables in this guide only reflect the ranges for pre-coordinated concepts; there may be post-coordination values that are not reflected in the tables. All MRCM values for concepts can be viewed via the public MRCM browser at .

SNOMED International creates precoordinated content in accordance with the MRCM. For postcoordinated content, extensions should review the MRCM. If the MRCM does not specify that a particular value is allowed for a given content type (e.g., using an observable entity value for |Component| in a postcoordinated expression), then it must not be used in that content type (e.g., postcoordinated expressions). The MRCM rules for postcoordination must be strictly followed. This is important for interoperability, being able to query the resulting content consistently, etc. However, the MRCM does provide the option for extensions to extend or adapt the rules in a controlled way if required (see the last section of ). This includes expanding the ranges and/or adding new attributes where required. This needs to be done carefully to ensure consistency and data integrity between editions.

There are special cases in the MRCM where an attribute may have two rows. This situation is caused by a new cardinality rule: a row for existing/legacy SNOMED CT content and a row for newly created content. The row that is applicable to new content will be marked by a "[New]" notation.

See .

SNOMED CT relies on the rules for usefulness to avoid excessive precoordination (see Scope section of Editorial Guide).

Approved precoordination patterns have been created and are available at: . For additional information about the fields used in precoordination, see: .

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The purpose of annotations is to provide a formal means to represent additional information about a SNOMED CT component (concept, description, relationship) or as a member of a reference set.

Annotations are:

• a form of metadata

• optional and non-defining

• constructed by following the Object-Attribute-Value pattern and stored either in annotation refsets or relationship files.

Each annotation uses a subtype of 1295447006 | Annotation attribute (attribute)| to represent the type of annotation with an annotation attribute value.

Attribution - Attributing credit to the source of information

For example,

• Inserm Orphanet attribution annotation at 1332326002 |Isolated cleft lip (disorder)|

Annotations can be:

• added to both new and legacy concepts.

  • For legacy concepts, attribution may only be added if there is a change to the modeling of the concept to support the collaborating organization's definition.

• added in the international edition or extensions.

Annotations in annotation refsets can be found by using ECL queries for refset members. Currently, there is only data in the refset called Component annotation refset with string value, so the following ECL query yields all SNOMED CT concepts currently with an annotation:

The ECL query can filter the members via ^1292992004 {{ M value="enter annotation string" }}

• For example,

Annotation length is restricted up to 4000 characters and are represented by the String data type which allows URL, number, and text for annotation values. Each annotation attribute should state the allowed values.

For example,

• If an attribute is only allowed for taking numbers, then URL or text should not be used for its values, because numbers are saved in different formats; numbers are saved with a prefix # and text is quoted.

The following are documented in the respective annotation guidance, if applicable.

• Maintenance process

• Validation for annotations, such as spell check

• Annotation cardinality - Most attributes will be 0..1 but some may allow multiple values.

See also for more information.

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A qualifying characteristic is expressed by an attribute-value pair. The attribute may have one value, from a range of values, based on the domain's concept model. If a particular qualifying characteristic is applied to a concept, the resulting expression represents a more tightly defined subtype of that concept.

For example,

• It might be possible to qualify a disorder such as

  53084003 | Bacterial pneumonia (disorder)| according to its clinical course (373933003 | Acute onset (qualifier value)| or 90734009 | Chronic (qualifier value)|) or severity (255604002 | Mild (qualifier value)|, 6736007 | Moderate (severity modifier) (qualifier value)|, or 24484000 | Severe (severity modifier) (qualifier value)|)

• 125605004 | Fracture of bone (disorder)| can be refined by qualifying it with 12611008 | Bone structure of tibia (body structure)| to represent the concept 31978002 | Fracture of tibia (disorder)|

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Cardiologists noted confusion in the placement of Conduction disorder of the heart (disorder) as a broad grouping that subsumed arrhythmias and heart blocks. In common usage arrhythmia refers to a broad set of conditions that include conduction disorders, under which are heart blocks. The concept Cardiac arrhythmia (disorder) is a parent of Conduction disorder of the heart (disorder), and the active referent of the inactive concepts named dysrhythmia or arrhythmia.

For example,

• Arrhythmias, like 72654001 |Supraventricular arrhythmia (disorder)|, are under 698247007 |Cardiac arrhythmia (disorder)|

Conduction disorders include heart block, AV block, bundle branch block, conduction delay, and conduction defect, like 418341009 | Atrioventricular conduction disorder (disorder) |. Other arrhythmias were moved from under 44808001 |Conduction disorder of the heart (disorder)| and placed under 698247007 |Cardiac arrhythmia (disorder)|.

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The term enteritis is broad and commonly refers to inflammation of the intestine, especially the small intestine. However, in some conditions, e.g. phlegmonous enteritis and regional enteritis, the term enteritis refers to any part of the digestive tract.

Thus, all descriptions of enteritis must stipulate the specific body structure that is affected to avoid potential misinterpretations and incorrect modeling.

For example,

• Enteritis of intestine

• Enteritis of small intestine

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There are two types of abscesses:

1. septic

2. sterile

Most abscesses are septic, which means that they are the result of an infection.

If a concept's meaning, based on its FSN and text definition, does not specify whether the abscess is sterile or septic, then the concept should not be modeled as septic.

This Editorial Guide is used for Education Purposes Only. It is used in the Authoring Courses and Certifications. It is based on the January 2026 Editorial Guide.

This Editorial Guide is used for Education Purposes Only. It is used in the Authoring Courses and Certifications. It is based on the January 2026 Editorial Guide.

The SNOMED CT Editorial Guide provides the information necessary to model concepts in SNOMED CT.

These guidelines should be applied to new content. While there are many concepts in the existing content that are not in compliance with this guidance, the process of correcting existing content will be carried out as time and resources permit.

SNOMED CT is distributed in sets of electronic files. Supporting software tools are not necessarily provided directly by SNOMED International.

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In addition to the general naming conventions below, please also see any applicable naming conventions for specific hierarchies in their respective .

Generally, names should:

• Be consistent and reproducible

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Set of structures through which lymph flows. It includes 59441001 | Structure of lymph node (body structure) | and 83555006 | Structure of lymphatic vessel (body structure) |. It supports the categorization of findings, disorders and procedures that relate to the flow of lymph.

Set of structures with groups of lymphoid cells, including those in the intestines, marrow, liver, and other locations, and the lymph nodes, spleen, thymus, and tonsils and adenoids; excludes the lymph vessels. It supports categorization of lymphomas.

All of the lymphoid system, as well as the mononuclear phagocytic system; the immune system also includes cellular and sub-cellular components involved in cellular and humoral immunity.

Collection of true macrophages, distributed widely in the body (splenic and lymphoid sinusoids, liver Kuppfer cells, pulmonary alveolar macrophages, osteoclasts, macrophages in serous membranes, and microgliocytes); also endothelial cells that line hematopoietic tissues.

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In general, concepts are represented in the singular, rather than the plural.

• For example:

  • |Disorder of lung (disorder)|, not |Disorder of lungs|

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Defining characteristics represent the values of a range of relevant attributes. Depending on the nature of the concept, they may include etiology, topography, method, etc.

The attributes that can be applied depend on the domain of the concept. For example, a procedure may have a method, and a disorder may have an etiology, but a procedure cannot have an etiology, and disorder cannot have a method. Defining characteristics using a particular attribute will be applied consistently to all concepts to which it is relevant. Note that this design principle may not be fully realized for all attributes in each release.

Defining characteristics are represented as relationships. The fields are used as follows:

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SNOMED CT authors use a zero-based , proximal primitive approach when modeling or editing logical definitions of concepts, i.e., a concept is newly defined, as opposed to inheriting the definition from the parent and then refining it. This is accomplished by assigning the immediate proximal primitive parent and attribute relationships based on their relevance to the defining characteristics of the concept, again, instead of relying on inheritance and refinement of relevant attributes from immediate, sufficiently defined supertypes.

The steps are as follows:

1. The author states the proximal primitive supertype/s.

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Concepts that cannot be sufficiently defined by necessary conditions are called primitive concepts. Primitive concepts cannot have subtypes automatically assigned by the classifier, unless a sufficient condition for that concept exists. Relevant concepts that are subtypes of a primitive concept in the taxonomy must be manually assigned an IS A relationship to that concept.

When a primitive concept is a child of one or more concepts and a parent of one or more concepts, it is known as an intermediate primitive.

• For example,

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Many terms that refer to body systems or tracts are used imprecisely in clinical practice and in medical publications. Ambiguities frequently arise with many of these terms. We have made the following definitions and distinctions in order to achieve internal consistency of the terminology. We recognize that it may not be possible to get universal consensus for the names for each of these concepts. The goal is to be consistent and clear in defining the meaning of each concept and to allow users and system designers to present the terms that best reflect these meanings in their own implementations.

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The Concept Model is used to specify logical definitions of SNOMED CT concepts. It is based on a combination of formal logic and editorial rules and includes the attributes and values that may be applied to concepts.

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Key requirements that drive the design, development, and maintenance of SNOMED CT are as follows. They are related to:

1. Electronic health applications (most often electronic health records or EHRs)

   • Support for effective delivery of high quality healthcare to individuals and populations

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This section contains naming conventions for anatomical structures in SNOMED CT.

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Sufficiently defined

A concept is sufficiently defined if its defining characteristics are adequate to define it relative to its immediate supertypes. A sufficiently defined concept is defined in the context of its hierarchy. See main glossary entry for sufficient definition.

Primitive

A concept which is not sufficiently defined is primitive. A primitive concept is a formal logic definition that is inadequate to distinguish it from similar concepts. A primitive concept does not have enough defining relationships to computably distinguish it from more general concepts (supertypes).

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Distinguishing consistently between lump and mass can be difficult in diagnostic contexts, as the terms are often used interchangeably or lack precise definitions. As a result, lump and mass have, in certain conditions, been treated as synonymous.

Avoid using 'lump' in new content, where more specific terminology is available.

Lump should not be added as a synonym for mass concepts in the Finding or Disorder hierarchies. Existing legacy synonyms and concepts will remain unchanged.

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FSN

A Clinical finding/Disorder concept's fully specified name (FSN) must be specific, though the preferred term (PT) can be a more clinician-friendly, word-order variant.

FSN Pattern

The FSN must conform to a specific pattern of "Disease of x" where a specific body structure is involved. For the preferred term, end users can choose the desired description that conforms to common clinical usage.

For example,

• FSN: Disease of kidney (disorder)

• PT: Can be either 'Kidney disease' or 'Renal disease'

The use of -opathy is to be used in the preferred term, because the FSN is to be specific and explicit, and there are often various interpretations of -opathy. A term containing the suffix -opathy can only be used in the FSN if a definition is applied via the DEF description.

For example,

• FSN: Disorder of macula of retina (disorder)

• PT: Can be either 'Disorder of macula of retina' or 'Maculopathy'

The morphologic abnormality is named before naming the anatomical site.

For example,

• In 399525009 | Inflammation of ampulla of Vater (disorder)|, Inflammation is the morphologic abnormality and Ampulla of Vater is the finding site.

Descriptions for Clinical findings and Disorders should follow the naming guidelines for Body structures if they are to be used within the Clinical finding/disorder concept.

Concepts describing limbs are abundant, and the use of limb in the FSN and the synonyms of upper/lower extremity, arm/leg should be followed.

• For example,

  • 249945007 |Monoparesis of lower limb (disorder)|

Because the finding site is 61685007 |Lower limb structure (body structure)|, which follows the anatomical guidelines, the disorder concept reflects lower limb in the FSN, while using synonyms of Monoparesis of leg and Monoparesis of lower extremity.

The term cerebral is used in clinical language to mean both cerebrum , and more broadly, brain.

• If the condition is limited to the cerebrum, the FSN, PT, and finding site will reflect the cerebrum. A synonym will remain with the term cerebral.

• If the condition refers more broadly to the brain, the FSN, PT, and finding site will reflect the brain – unless the proper name of the condition uses the term cerebral , as in Cerebral palsy. A synonym will remain with the term cerebral if it is commonly used to refer to the condition.

The word disorder should be singular, so Disorder of nose , not Disorders of nose.

• When the concept is a general grouping of disorders of a body system, body site, or other broad category, the word disorder is preferred over the word disease for the FSN, e.g. Disorder of reproductive system , not Disease of reproductive system. This does not apply at the leaf level.

• For example,

  • 417683006 | Sickle cell-hemoglobin C disease without crisis (disorder)|

For naming conventions concerning surgical complications, sequelae, and late effects; see this section at .

The vast majority of existing X without Y concepts originated from ICD-9 with the specific meaning of "X disorder without mention of Y disorder". As the phraseology indicates a lack of data about disorder Y as opposed to a specific exclusion, this type of concept has not been included in ICD-10, nor proposed for ICD-11, except in the case of "Traumatic brain injury without open intracranial wound".

Addition of new X without Y concepts may only be made under the following conditions:

• The request for new content must be accompanied by a rationale as to the difference between "X disorder without Y disorder" and "X disorder"

• Approval of addition by the Chief Terminologist

For the most part, existing X without Y concepts will be inactivated as AMBIGUOUS with a historical MAY BE relationship to "X disorder". Exceptions to inactivation will be made on a case-by-case basis.

SNOMED international is no longer accepting new requests for concepts of the type – Requires [procedure/drug] (finding). These are administrative statuses rather than clinical findings, and this status should be represented outside of the terminology in the information model. The only exceptions relate to legacy content, and requests for subtypes of 723620004 |Requires vaccination (finding)| will continue to be accepted.

If the 363698007 | Finding site (attribute)| value of a concept is a body structure with "region" in its FSN, then the description of the finding site within the clinical finding concept's FSN should also include "region".

• For example,

  274205003 | Burn of eye region (disorder)| has a finding site of 371398005 | Eye region structure (body structure)|.

  • FSN: Burn of eye region (disorder)

  • PT: Burn of eye region

Previously, allergies caused by multiple substances were modeled by multiple causative agents suggesting that the allergy is caused by all those substances. However, when multiple substances are noted in the FSN, the intended clinical meaning is that a patient might be affected by one or more of these substances (or products containing them). To convey this meaning, these types of concepts should be modeled GCIs to represent the disjunctive meaning. e.g. 870731003 |Allergy to carbidopa and/or levodopa (finding)|

Allergic and nonallergic hypersensitivity (pseudoallergic) dispositions are the propensity to develop adverse allergic or nonallergic hypersensitivity (pseudoallergic) disorders. A description for any concept that names a substance or an organism should be consistent with the corresponding hierarchy description rules.

• FSN: Allergy to X (finding)

• PT: Allergy to X

For example,

• FSN: Allergy to abacavir (finding)

• PT: Allergy to abacavir

• FSN: Allergy to Artemisia vulgaris pollen (finding)

• PT: Allergy to mugwort pollen

FSN: Allergy to X and Y (finding)

PT: Allergy to X and Y

• X and Y in alphabetical order for concepts representing multiple substances

These disorders represent manifestations of pathologic processes that may result in abnormal structures (e.g., allergic rhinitis).

These disorders represent pathological processes that are defined as adverse reactions and allergic conditions with a pathological process of allergic or nonallergic hypersensitivity (pseudoallergic) process.

Contact hypersensitivity represents a response elicited by contact of the skin or mucous membranes with a substance. The response may be immune mediated (allergic) or nonimmune (irritant) using the pathological process contact hypersensitivity process (qualifier value).

• For example,

  • Contact dermatitis (disorder)

  • Irritant contact dermatitis (disorder)

An intolerance is the propensity to develop an adverse reaction to a substance. The nature of the adverse reaction can represent a variety of pathological processes but specifically excludes hypersensitivity (allergic and nonallergic hypersensitivity (pseudoallergic) reactions.

Due to the difficulty in precisely defining an intolerance pathological process, it is problematic to apply the model for hypersensitivity dispositions to defining intolerance to substance. For this reason, as well as the difficulty in associating a material agent with a disposition, substances are related to the intolerance disposition with the associated with attribute.

Identification of findings of inadequate or excessive intake of nutrients inconsistent with nutrient requirements and established reference standards includes nutrients with a variety of forms where applicable.

For example,

870465001 | Excessive intake of vitamin A and vitamin A derivative (finding)|

FSN: Excessive intake of vitamin A and vitamin A derivative (finding)

PT: Excessive intake of vitamin A and vitamin A derivative

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The anticipated benefits of SNOMED CT are derived from use of information to support effective delivery of high quality healthcare to individuals and populations.

Individuals

Aide-memoire for clinicians

Clinically relevant information in an electronic health record acts as an aide-memoire for the clinician, enabling recall of previous interactions.

Structured data entry

Structured data entry enhances the value of an electronic health record in various ways. It may:

• Simplify recording of frequently collected data

• Ensure that information is collected in a reliable and reproducible way

• Help clinicians to think logically about a patient's condition

Clinical applications may combine several data entry methods. Some of the most commonly used methods are as follows:

• Searching a coded terminology for matching terms using words or phrases

• Navigating a hierarchical structure to refine or generalize meanings

• Using templates or protocols to record structured information; may be based on answers to questions or values entered on a data entry form

Data entry may require selection from a list. Such lists must be manageable in size and appropriate to the needs of the user.

• A multilingual, multidisciplinary terminology requires mechanisms that limit and/or prioritize access to terms and codes in ways that are appropriate to:

  • Languages and dialects

  • Countries, organizations, disciplines, specialties, and users

When a code is entered in a record it may require structured entry of additional qualifying information.

• Qualifying information may be coded.

  • For example,

    • The code named removal of kidney may require a statement of laterality.

To meet all the needs for coded structured data entry in a health record, a terminology must have an adequate scope.

• The main body of SNOMED CT covers the required scope.

  • It may be difficult to meet the needs of some organizations, specialties, and users; they may need specific terms or codes to meet their own operational requirements. Therefore, SNOMED CT is structured to allow for additions to meet specific needs.

A clinical terminology requires frequent changes including new codes, terms, and relationships between codes. Changes may be required due to new:

• Health risks

• Health and disease process information

• Drugs, investigations, therapies, and procedures

The presentation of clinical information may:

• Highlight key information and indicate links between items, thus helping clinicians understand patients' conditions.

• Be determined entirely by record structure without regard to the terminological resource (e.g.,may be in chronological order, by author, or by the type of recorded event).

• Be enhanced based on its semantic content (e.g., grouping procedures, investigation results, or observations relevant to a particular disease process).

Interfaces between recorded clinical information and appropriate decision support tools and reference works may assist the clinician in selecting diagnostic tests, making diagnoses, and choosing treatment. Decision support requires selective retrieval and processing of information in an individual health record to determine whether the patient has particular characteristics relevant to the decision support protocol. The algorithms for establishing the presence of characteristics should include relationships between coded meanings and other aspects of record structure. Performance is also important, as decision support algorithms are typically run in real-time during data recording. Decision support algorithms may:

• Depend on numeric or other values (and their units) associated with particular observations

• Include the context in which information is recorded, e.g., the date of recording and any stated relationships between individual items of information

• Include information such as age, sex, clinical conditions, findings, surgical procedures, medication, and social/environmental factors, such as occupation

Effective delivery of high quality healthcare to individuals requires communication between those involved in providing care. This requires communication within and across teams or organizations.

The primary objective of many clinical communications is to convey information from human to human. Communications with this purpose should include human-readable text. Relying on text from coded data is not recommended. Coded data is therefore not relevant to the requirement for human-to-human communication.

A receiving application may process clinical communications. This information may need to be retrieved and processed to meet terminology requirements. To meet terminology requirements, messages and other means of electronic communication must permit the communication of SNOMED CT identifiers and associated structures.

Communication specifications, such as those produced by HL7 and CENTC251, define the structures to meet requirements. The coded information is used in two distinct situations:

• Coded elements that must be filled with codes enumerated in the specifications. The codes enumerated in the specifications generally communicate, mission critical features of the message. Some of the enumerated codes and the codes in a clinical terminology may have overlapping meanings.

• Coded elements that are populated with clinical codes from appropriate coding schemes. The open coded elements may require the full expressiveness of a terminology. Some of the open coded elements may be restricted to codes that express particular types of meaning.

  • For example,

There are two situations in which communication of coded information may be of value for human-to-human communication. They are where:

• The storage capacity or communication bandwidth is restricted. Receiving applications must contain (or have real-time access to) a table listing the text description associated with each code.

• The translation between the languages of the sender and the recipient is needed. A coded representation of a meaning may allow the appropriate description in the recipient's language.

Recording a particular code may trigger a communication. And, receipt of a code, may trigger specific processing in the receiving application.

• For example,

  • Recording a decision to prescribe a medicine might trigger an electronic prescription sent to the pharmacy. Receipt of such a prescription might trigger dispensing and stocking activities.

The relationship of a trigger is an additional characteristic of a code that may be context dependent.

Patients may wish to view, and comprehend, their own records. For SNOMED CT to meet this requirement, the inclusion of patient-friendly terms should be considered. However, this requirement should not take precedence over accurate professional terminology.

Patients may also be allowed to contribute to their own records, i.e., be users of SNOMED CT.

• For example,

  • Patients with diabetes may monitor and record their blood glucose levels.

The provision of effective high-quality care to populations requires an understanding of the state of health and healthcare needs of that population. Information recorded about individual patients must be available for analysis to determine trends.

• It must be possible to analyze data recorded with SNOMED CT.

Population trends are usually monitored at a higher level, using codes that are more general than those used in individual patient records. This may be accomplished through one or both of the following methods:

• Using hierarchical relationships and/or equivalences defined within SNOMED CT.

• Mapping SNOMED CT codes to codes in appropriate classifications.

Appropriate analysis of information requires reliable and reproducible queries.

• The scope of SNOMED CT must cover the types of information relevant to analysis.

• Analysis may require data about multiple clinical characteristics. Queries must account for both the terminology and the record structure.

The requirements for analysis of quality of service are similar to those for analysis of health needs. The main difference is that the scope of the analysis must be extended to cover consultations, referrals, procedures, medications, and other interventions.

The requirements for research are also similar to those for analysis of health needs, however, there is a need to allow for:

• Recording interventions in ways that do not compromise blind and double blind trials.

• Adding SNOMED CT content for experimental observations or treatments, which may never require permanent addition to the terminology.

The management and funding of healthcare delivery often depends on recording and reporting of particular information, e.g. bundled or packaged care. Automating this process offers a way of reducing bureaucratic overhead, i.e. mapping clinical information recorded with SNOMED CT to appropriate forms.

Some information required for management and funding purposes is specifically related to claims for particular events or services.

• For example,

  • Funding general practitioners in the NHS is dependent on meeting immunization administration and cervical cytology screening targets.

The scope of SNOMED CT must be adequate to meet these needs, or must be capable of extension to meet these needs, without presenting irrelevant terms or coded meanings to those not requiring them.

Organizations, such as WHO and some government bodies, require specific data related to healthcare statistics. Organizations should be able to use clinical information recorded with SNOMED CT. When this is not possible, the clinical information should at least support their manual generation. Using structured data entry allows for direct mapping to statutory national and international classifications such as ICD, CPT, OPC, etc.

Population-based preventive care should be offered to specific groups, based on sex, age, medical history, and other factors. Health information applications based on information recorded with SNOMED CT can be used to identify patients, so they can be offered appropriate care.

This Editorial Guide is used for Education Purposes Only. It is used in the Authoring Courses and Certifications. It is based on the January 2026 Editorial Guide.

A definition is a textual description applied to some SNOMED CT concepts that provides additional information about the intended meaning or usage of the concept. Definitions are not mandated and are considered for addition on a case-by-case basis, and if required, to differentiate a concept from its related concepts.

Adding a definition to a concept provides additional clarity on its context of use. It enhances the definition provided by the modeled relationships whereby a term can be sufficiently defined logically, but the words, which is how many look for and interpret meaning, may imply more or less specificity.

Definitions must:

• be written as complete sentences,

• begin with a capital letter,

• end with a period,

• apply a case sensitivity of Entire term case sensitive (CS).

For example,

• The definition for the concept 11530004 | Brittle diabetes mellitus (finding)| is:

  • Frequent, clinically significant fluctuations in blood glucose levels both above and below levels expected to be achieved by available therapies.

The language acceptability default for a single Definition description is Preferred. A definition with varying US and GB English descriptions are each applied with the respective language acceptability.

For example,

A text definition should be considered where a concept references the obscure or unusual. As an example, raised blood pressure is a commonly used phrase, which, in itself, is ambiguous. Raised can mean: 1) higher than a previous measurement, 2) on the high side of normal range, or 3) above reference range. Because of that ambiguity, a full definition created by logical model may be impossible, so a text definition could be used to encourage consistent use of the term.

The following principles for definition creation are summarized below from ISO-704, Terminology work — Principles and methods :

In summary, if a term may be interpreted in multiple ways, but is intended to mean only one way in SNOMED CT, it needs a definition. However, ultimate source of truth for meaning remains with the FSN.

This Editorial Guide is used for Education Purposes Only. It is used in the Authoring Courses and Certifications. It is based on the January 2026 Editorial Guide.

Skin, skin-associated mucosa

This is an example of a body structure that is used to group related terms.

The concept 707861009 |Structure of skin and/or skin-associated mucous membrane (body structure)| intentionally employs disjunction (inclusive Or). It includes structures in the deep layers, but excludes non-skin mucosal epithelium, e.g., bronchial, gastrointestinal, and genitourinary sites of squamous cell neoplasms. The 400199006 |Structure of skin and/or surface epithelium (body structure)| concept is used to represent the sites of these neoplasms.

Skin and/or skin-associated mucosa is intended for use in dermatology. It is not intended to subsume all mucosal structures, which are under Mucous membrane structure (body structure).

Skin regions, skin of <body part>

Since the phrase skin of finger can mean some or all of the skin of finger (if interpreted as a structure, rather than entire in the The StructureEntirePart (SEP) model , we could use IS-A to represent the relationship between skin of finger and skin of hand. Thus, skin of finger IS-A skin of hand, IS-A Skin structure of upper limb, IS-A skin region. The word region is not used in all of these names, because it may refer to the entire region or a part of a region.

Formal definitions of scalp include layers beneath the skin. Therefore we make a distinction between 41695006 |Scalp structure (body structure)| and 43067004 |Skin structure of scalp (body structure)|.

There are at least three different use cases and meanings, and thus categories, for the phrase soft tissue. They include:

• Tumors. Soft tissue gives rise to similar types of neoplasms of mesenchymal stem cell origin, generally called soft tissue neoplasms. This accounts for the inclusions/exclusions of the category. Non-neoplastic masses arising in soft tissue are included in the WHO Classification of Soft Tissue Tumours.

  • For tumors, soft tissue is defined as non-epithelial extraskeletal tissue of the body, exclusive of the mononuclear phagocyte system, glia, and supporting tissue of various mesenchymal organs. Other explicit inclusions are: fibrous tissue, fascia, ligaments, tendons, tendon sheaths, synovia, bursae, skeletal muscle, smooth muscle, fatty tissue, adipose tissue, blood vessels, lymph vessels, peripheral nerves, sympathetic and parasympathetic nerves, and ganglia, as well as subcutaneous tissue. Skin, skeletal cartilage, pleura, and the pericardium, peritoneum, central nervous system, endocrine glands, and viscera are excluded.

This Editorial Guide is used for Education Purposes Only. It is used in the Authoring Courses and Certifications. It is based on the January 2026 Editorial Guide.

Draft guidance

See the background, use cases, and examples for general concept inclusion axioms as well as explanation of the definition status at General Concept Inclusion 0.01.

Authoring Platform User Guide for GCIs

Reference the Authoring - Description Logic (DL) Support Features for technical information describing how to add an additional axiom and general concept inclusion.

GCI display in the browser

A concept with GCIs will display in the browser in the stated view only.

For example,

Below is 417163006 | Traumatic or non-traumatic injury (disorder)| in the stated view with the GCIs appearing to the right of the concept:

Here is the same concept in the inferred view without the GCIs appearing:

General concept inclusions allow multiple definitions of a concept. A group of subtypes may be defined using GCIs and be considered subtypes of the parent concept without fully defining that parent concept. That parent concept could have multiple definitions, each of which is valid but none of which completely describes the parent concept on its own.

When modeling a concept intended to be a subconcept of a GCI concept defined by General Concept Inclusion (GCI) axioms, it is unnecessary to state the GCI concept as a parent if the logic of the concept being modeled is already covered by a GCI axiom. This holds true even if the GCI-modeled concept is primitive, as the GCI axioms ensure that the correct subsumption relationship is inferred regardless.

• For example,

  • 281372009 |Lumbarized first sacral vertebra (disorder)|

The diagram below shows Lumbarized first sacral vertebra (disorder) incorrectly modeled on the right, with a stated primitive GCI-modeled parent of Transitional lumbosacral vertebra (disorder). Transitional lumbosacral vertebra (disorder) is modeled with a GCI, as notified by the salmon pink color. The left side of the diagram shows the inferred view with two parents.

The GCI-modeled primitive concept, Transitional lumbosacral vertebra (disorder), is unnecessary to state as a parent. The diagram below shows correct modeling of Lumbarized first sacral vertebra (disorder) with the absence of Transitional lumbosacral vertebra (disorder) as a parent, and yet the inferred view diagram on the left is still the same as compared to the incorrectly modeled diagram above.

Alternatively, if a GCI-modeled parent will not subsume an appropriate child concept, then the GCI-modeled concept should be stated as a primitive supertype.

Finally, the example below of 82271004 |Injury of head (disorder)| illustrates a concept with a GCI-modeled supertype of 417163006 |Traumatic or non-traumatic injury (disorder)|. In this case, the concept Injury of head (disorder) is sufficiently defined.

Though most are primitive, it is possible to define concepts modeled with GCIs. A concept must continue to meet the necessary conditions in order to be considered defined. GCIs can be added to extend the subtypes a defined concept will infer when appropriate.

• GCIs are not restricted to particular hierarchies; they can be used as applicable in any hierarchy that has a concept model.

• The Authoring Platform does not currently have the ability to create templates that include GCIs.

• A concept which has a stated "is a" relationship to a concept with GCIs will need to have GCIs added to it directly if GCIs are required to appropriately represent the concept. GCI axioms are not inherited from supertype to a subtype concept.

This Editorial Guide is used for Education Purposes Only. It is used in the Authoring Courses and Certifications. It is based on the January 2026 Editorial Guide.

For hierarchies with a concept model, the usefulness of fully-defined groupers is limited to convenience groupings based on particular use cases. They may be added if they provide demonstrable benefit to organizing and navigating the terminology.

Grouper concepts provide a definition for subtypes that are always and necessarily true. The grouper concept must be sufficiently defined and clinically useful for the purpose of organizing content for an intensional reference set (e.g. disease of colon and all of its descendants) or in Expression Constraint Language (ECL), << 128524007 | Disorder of colon (disorder)|.

Navigational concepts

Grouper concepts should not be confused with navigational concepts. Navigational concepts were created to group other concepts without explicit regard for defining attributes (since there were none). Their purpose was to provide top level groupers for subsets and reference sets used in implementations. Because the Reference Set mechanism is now available, there is no longer a need for navigational concepts in the International Release; however, they can be added at the national or lower level.

In the past, there was an indiscriminate move of concepts in and out of the navigational concept hierarchy based arbitrarily on use cases by those users organizing concepts based on a particular classification that was wanted. The navigational concept hierarchy was useful to group things into a particular domain. The problem is that many of these are domain-specific and cannot be generalized. For example, mosquito-borne diseases will vary depending on the location of the user. It is difficult to classify the complete instance of these as well. Potential children would have to be manually assigned.

Because this is a primitive hierarchy and subtypes will not auto classify, much work would be required to reorganize hierarchies and maintain the use of navigational concepts. Inactivating concepts may be met with requests to create intermediate primitives. The Content Managers Advisory Group [CMAG] at 2020 Use of navigational concepts is being consulted regarding current use of navigational concepts.

As 363743006 | Navigational concept (navigational concept)| is within the 370115009 | Special concept (special concept)| subhierarchy, please see that section of the Editorial Guide at Special Concept.

Intermediate primitive groupers add a substantial management burden, thus, are discouraged. They may however be added on a case-by-case basis with approval from the Head of Terminology when, for example:

• The concept model is not robust enough to support the full definition of a subset of terms, e.g., genomics (i.e., genetic diseases for which we cannot state, the majority of cases of this disease present with X).

• There are variances in the clinical manifestations.

If an existing intermediate primitive concept cannot be sufficiently defined and has only one subtype, is not used to model another concept nor demonstrably clinically useful, it should be inactivated.

A grouper concept that is added to SNOMED CT must adhere to the following rules:

• The concept must not be created with the hierarchical tag (navigational concept).

• The concept must use the semantic tag for the relevant hierarchy, e.g., (finding), (procedure).

• The concept must not have stated subtypes. All subtypes must be inferred by the classifier.

Where grouper concepts already exist, the following criteria apply:

• If it can be sufficiently defined, remodel it, and reassign existing stated subtypes to a new proximal primitive parent.

• Identify primitive concepts that cannot be sufficiently defined for additional review.

This Editorial Guide is used for Education Purposes Only. It is used in the Authoring Courses and Certifications. It is based on the January 2026 Editorial Guide.

The headings in this section are the requirements identified in Desiderata for Controlled Medical Vocabularies in the Twenty-First Century by J.J. Cimino published in Methods of Information in Medicine 1998:37:394-403. Following each, is an explanation of the way in which SNOMED CT meets the requirement.

Content, content, and content

SNOMED CT content must be adequate both in scope and quality and must:

• Cover a wide variety of domains and different organizational needs, clinical disciplines, and medical specialties

• Meet the needs of an expanding scope, while retaining quality, with a structured systematic approach

Codes must have one meaning (nonvagueness) and no more than one meaning (nonambiguity). These characteristics are sometimes called concept orientation , but SNOMED CT deprecates the use of the word concept to describe codes or their meanings.

A code and its meaning may be expressed by more than one term. The terms vary between languages and dialects. In any language or dialect there may be several synonymous terms.

Once assigned a meaning, a code must not change its meaning. Refinements, due to changes in the state of knowledge, may lead to inactivation of codes from SNOMED CT. An inactivated code may be replaced by a new, more precisely defined code.

The structure of an identifier (code) should not contain any semantic information about its meaning or relationships.

SNOMED CT supports multiple hierarchies. A code may have more than one hierarchical parent and various paths to its root code.

When possible, the meaning of codes should be formally defined by relationships to other codes.

Codes with the phrase, not elsewhere classified , are not allowed in SNOMED CT. However, many classifications contain terms with this phrase. A term with not elsewhere classified includes general variants that are not specifically represented. The meaning of such a code may change over time. As codes with more specific meanings are added, this narrows the codes included in the not elsewhere classified codes.

Different users will need to express more or less finely granular meanings. SNOMED CT:

• Must accommodate a wide range of levels of detail

• Must recognize the relationships between meanings at different levels of granularity

• Should allow selection of codes that include navigation to other codes with more or less finely grained meaning

The view of a code's meaning, with multiple hierarchical parents, should not depend on reaching it by following the hierarchy from a particular parent.

The meaning of a code in a patient record may be altered by its context. Standards for patient record architectures and modeled healthcare communication are changing. The role of SNOMED CT in the context of these structures should be evaluated and appropriate recommendations made.

Terminologies need to change over time. SNOMED CT should implement these changes in ways that are well-documented and tracked and that provide a path for systems and users.

The same information can often be coded in different ways. A controlled terminology, that has an adequate scope, cannot exclude this possibility. Instead it should facilitate recognition of equivalent terms.

This Editorial Guide is used for Education Purposes Only. It is used in the Authoring Courses and Certifications. It is based on the January 2026 Editorial Guide.

See glossary for definition here:

For some, but not all concepts, the proximal primitive parent is a top level concept, e.g., Procedure.

The proximal primitive supertype may also be an intermediate primitive concept located between the top level concept and the concept in question.

There may be more than one proximal primitive supertype for a concept.

The approved modeling approach is to use:

• Proximal primitive supertypes

• Attribute-value pairs sufficient to define the meaning

  • An attribute-value pair is explicitly stated for the concept, even if it is already present for a supertype concept.

The classifier infers all appropriate proximal supertypes. With sufficiently defined concepts the subtypes are also inferred.

• For example,

  • The proximal primitive supertype for this concept is

    71388002 | Procedure (procedure)|. It has been modeled with one stated supertype and two attribute value pairs in a relationship group.

The inferred view shows the logical definition of the concept. By using the stated relationships (for this concept and other concepts currently in the terminology), the classifier infers three defined proximal supertypes:

• Radiography of humerus (procedure)

• Computed tomography of upper arm (procedure)

• Computed tomography of bone (procedure)

Where more than one potential primitive supertype is identified for a concept, authors should check the primitive supertypes for subsumption of one or more other primitive supertypes. Any subsuming concept is not a proximal primitive supertype.

• For example,

  • There is more than one potential primitive supertype for

    421095001 | Allergic disorder by body site affected (disorder) |. However, 64572001 | Disease (disorder) | is subsumed by 404684003 | Clinical finding (finding)|, therefore 64572001 | Disease (disorder) | is the proximal primitive supertype concept.

For information on the effect of GCIs on modeling primitive supertypes, see (GCIs).

This Editorial Guide is used for Education Purposes Only. It is used in the Authoring Courses and Certifications. It is based on the January 2026 Editorial Guide.

Roman numerals versus Arabic numbers

Use the most common representation found in literature for the fully specified name. Use the alternative representation as a synonym, if it is also represented in the literature. If neither representation is common, use the Arabic representation.

For example, in the AMA Manual of Style, cancer stages are expressed with the use of capital Roman numerals: stage I, stage II, stage III, stage IV. The term, "stage 0", usually indicates carcinoma in situ. Histologic grades are expressed with Arabic numerals, e.g., grade 2.

Numeric ranges

In general, content that depends on numeric ranges should not be used for precoordination.

• For example,

  • There may be too many possibilities

    • A finding of number of lesions might have ranges of 1, 2 to 5, and greater than 5; 1 to 2, 3 to 10, and greater than 10, etc.

  • There may be possible changes to reference ranges or systems of units

This Editorial Guide is used for Education Purposes Only. It is used in the Authoring Courses and Certifications. It is based on the January 2026 Editorial Guide.

In modeling some bacterial disorders, there will be situations where either the organism or the toxin (substance), or both values, are required for the causative agent attribute. The decision is often determined by whether or not the bacteria are considered endotoxins or exotoxins. The most common exotoxins are:

• Botulinum Toxin

  • Enterotoxin

  • Cholera Toxin

  • Diphtheria Toxin

  • Tetanospasmin

Exotoxins are more lethal in comparison to endotoxins, but there are vaccines against many exotoxins whereas there are no vaccines against endotoxins. There can be instances where an infection is present but the disease-causing toxins are not; in this case, model the concept only with the organism and not the toxin substance.

Example,

• 276202003 |Infection caused by Clostridium tetani (disorder)| is modeled with a causative agent of 30917009 |Clostridium tetani (organism)| only.

In the situation where a disease is caused by both the infection and the associated toxin, model with both the causative agent and the toxin substance.

Example,

• 76902006 |Tetanus (disorder)| is modeled with a causative agent of 30917009 |Clostridium tetani (organism)| as well as 26159005 |Clostridium tetani toxin (substance)|.

This Editorial Guide is used for Education Purposes Only. It is used in the Authoring Courses and Certifications. It is based on the January 2026 Editorial Guide.

SNOMED CT is intended to be used in healthcare:

• To provide effective and comprehensive coverage of terms

• As a terminological resource

• For implementation in electronic health applications

The purpose of SNOMED CT is to represent clinically relevant information reliably and reproducibly in electronic health applications, (most often electronic health records or EHRs) to support:

• Delivery of multidisciplinary, high-quality healthcare to individuals and populations

• Optimal retrieval, processing, and rendering of clinical information

• Effective use of clinical information consistently and reproducibly

The overall semantic interoperability of electronic health applications is achieved through the combined functioning of the information architecture of the application and the terminology that populates it. A basic principle of SNOMED CT is to create and maintain semantic interoperability of clinical information. Semantic interoperability is the capability of two or more systems to communicate and exchange information. Each system should be able to interpret the meaning of, and effectively use, received information. To achieve this goal, the meaning of the information must be agreed upon, consistent, and clearly expressed.

Context is an important part of representing clinically relevant information.

When entered in an EHR, concepts in the Procedure and Clinical finding hierarchies have the following default contexts.

• The procedure has actually occurred (versus, e.g. being planned or cancelled) or the finding is actually present (versus, e.g. being ruled out or considered)

• The procedure or finding refers to the patient of record (versus, e.g, a family member)

• The procedure or finding is occurring now or at a specified time (versus some time in the past)

When a concept is entered into an EHR, the information in the health record structure or its information model, can provide the context.

In addition to using the record structure to represent context, there may be a need to override the defaults and specify a particular context using the formal logic of the terminology. For that reason, SNOMED CT has developed a context model, i.e Situation with explicit context, to allow users and/or implementers to specify context using the terminology, without depending on a particular record structure. The Situation with explicit context hierarchy, and various attributes assigned to concepts in the hierarchy, accomplish this.

Designers and implementers of electronic health applications need guidance to identify which fields within their record structure will critically affect the meaning of concepts. They require open strategies to preserve meaning if concepts are retrieved or transferred and to allow detection of equivalence to constructs derived from alternative approaches.

(see also Situation with Explicit Context section)

This Editorial Guide is used for Education Purposes Only. It is used in the Authoring Courses and Certifications. It is based on the January 2026 Editorial Guide.

Multiple x morphologies, such as 125291005 |Multiple cysts (morphologic abnormality)|, are currently subtypes of the “X” morphology. The “X” morphology concept represents a class rather than a singular instance, and this arrangement follows the open world assumption of the description logic in SNOMED CT.

• For example,

  • Cyst of upper eyelid does not mean a single cyst on a single upper eyelid. It represents a class of cyst condition that at least appeared in an upper eyelid. This class would also include a cyst condition involving both upper and lower eyelids.

  • A similar example is how |Retinitis of bilateral eyes (disorder)| is a subconcept of |Retinitis of left eye (disorder)| and |Retinitis of right eye (disorder)|.

Having the Multiple X morphologic abnormality concept as a subtype of the “X” morphology concept allows the disorder concepts defined by these “multiple X” morphologies to be sufficiently defined. One drawback of the current format is that classification results are not complete.

• For example,

  • Multiple cysts of eyelid would not subsume cysts of upper and lower eyelids in the current concept model.

This Editorial Guide is used for Education Purposes Only. It is used in the Authoring Courses and Certifications. It is based on the January 2026 Editorial Guide.

When modeling a concept requiring two role groups with the same finding site/body structure but two different morphologies (because a combined morphology does not exist), then those two morphologic abnormalities can be combined to create a new single, combined |(morphologic abnormality)| concept. Keep the newly created morphologic abnormality concept primitive as all morphologic abnormality concepts should be primitive. Limit the combination to two morphological concepts into a single concept; combining more than two morphological concepts into a single combined concept is not permitted.

Example, If 400067002 |Acantholytic epidermal nevus (disorder)| had the same Finding site of |Skin structure (body structure)| with two different morphologic abnormalities of |Epidermal nevus (morphologic abnormality)| and |Acantholysis (morphologic abnormality)|, then those two morphologic abnormality concepts can be combined to create a single, primitive, morphologic abnormality concept of |Acantholytic epidermal nevus (morphologic abnormality)|. This will prevent modeling with two relationship groups.

Instead of modeling as per this diagram in the stated view with two morphologies of the same finding site:

Model as in the stated view of this diagram with a combined morphology:

Morphologies can be combined to create a single morphologic abnormality concept where doing so creates a specialization of the morphology e.g. 55075001 |Bleeding ulcer (morphologic abnormality)|. Where morphologies are different e.g. abscess and cellulitis, they can not be combined.

Combining morphologies to create a specialization is done when modeling a concept that requires two role groups with the same body structure and two morphology values. Creating a combined morphology concept enables one role group to be used.

Subtypes of 108369006 |Neoplasm (morphologic abnormality)| are not to be combined. These morphologies represent histological cell types that are recognized internationally by pathologists, classified by WHO, and aligned with the ICD-O classification.

This Editorial Guide is used for Education Purposes Only. It is used in the Authoring Courses and Certifications. It is based on the January 2026 Editorial Guide.

Concept

A concept is defined as a clinical idea to which a unique concept identifier has been assigned. Concepts are associated with descriptions that contain human-readable terms describing the concept.

A term is defined as a human-readable phrase that names or describes a concept. A term is one of the properties of a description. Other properties of a description link the term to an identified concept and indicate the type of description, e.g. Fully Specified Name, Preferred Term, Synonym.

Concepts are linked to their more general parent concepts directly above them in a hierarchy. More general meanings, are usually at the top of the hierarchy. Descending levels of the hierarchy contain more specific or specialized meanings.

Concepts are logically defined by their relationships to each other.

In SNOMED CT, the default meaning of a concept is defined above. However, a concept may have other meanings in SNOMED CT, such as an:

• Abbreviated name for the concept identifier. For clarity, this is should be referred to as an identifier(ID), code, or concept identifier (ID).

• Idea or class of real-world entities (common usage meaning). For clarity, this is should be referred to as a clinical idea , clinical meaning, or code meaning.

The concept file includes a special concept referred to as the root concep t. It is the single concept that is at the top of the SNOMED CT concept hierarchy. All other concepts are descended from this root concept via at least one series of relationships of the Relationship type 116680003 | Is a (attribute)| , i.e. all other concepts are regarded as subclasses of this concept. The root concept code is . All other SNOMED CT concepts are subtypes of the root concept. Unlike other SNOMED CT concepts, the root concept is not a subtype of any other concept.

Concepts that are directly related to the root concept by a single relationship of the Relationship type 116680003 | Is a (attribute)| are referred to as top-level concepts. All other concepts are descended from at least one top-level concept via at least one series of relationships of the Relationship type 116680003 | Is a (attribute)| , i.e. all other concepts represent subclasses of the meaning of at least one top-level concept.

A concept that is directly related to the root metadata concept, 900000000000441003 | SNOMED CT Model Component (metadata)| by a single relationship of the relationship type IS_A. All metadata concepts are descended from at least one top-level metadata concept via at least one series of relationships with Relationship type IS_A. Metadata codes represent structural information about the terminology itself. The top-level metadata concepts represent broad groups of metadata.

Subtype relationships provide the main semantic hierarchy that relates concepts to one another. All active concepts, except the root concept, have subtype relationships with one or more concept. Each of these relationships indicate that a concept is a subtype of another concept.

Subtype relationships are expressed in the same way as other SNOMED CT relationships. They are identifiable by their fully specified names, e.g 116680003 |Is a (attribute)|.

For example,

• 53084003 |Bacterial pneumonia (disorder)| is a subtype of 233604007 |Pneumonia (disorder)| because it is a subtype of 312342009 |Infective pneumonia (disorder)| which is also a subtype of 233604007 |Pneumonia (disorder)|

This Editorial Guide is used for Education Purposes Only. It is used in the Authoring Courses and Certifications. It is based on the January 2026 Editorial Guide.

Knowledge representation in SNOMED CT involves modeling what we know about concepts to be necessarily true. Concepts are logically defined by their relationships to each other. Some knowledge provides valuable clues to the diagnostician, while not necessarily always present, i.e. it is uncertain or probabilistic knowledge. Attempts to capture probabilistic or uncertain knowledge are out of the scope of SNOMED CT.

22298006 | Myocardial infarction (disorder)|

Its terminological knowledge includes the following:

IS A: 
64572001 | Disease (disorder)|

Finding site: 
74281007 | Myocardium structure (body structure)|

Associated morphology: 
55641003 | Infarct (morphologic abnormality)|

These additional pieces of knowledge are variably present and therefore represent uncertain or probabilistic knowledge about myocardial infarction:

• Crushing substernal chest pain

• Diaphoresis

• Arrhythmia

• ST-segment elevation on EKG

• Elevated cardiac enzymes

Another example:

Its terminological knowledge includes the following:

These additional pieces of knowledge are variably present and therefore represent uncertain or probabilistic knowledge about appendicitis:

• Central abdominal pain that migrates to the right lower quadrant

• Rebound tenderness over McBurneys point

• Anorexia

• Nausea

This Editorial Guide is used for Education Purposes Only. It is used in the Authoring Courses and Certifications. It is based on the January 2026 Editorial Guide.

Names

The use of the name of a clinical form or tool or of a brand name drug will usually not infringe on the copyright. However, caution should be exercised by implementers who wish to use trademarks in a commercial context, i.e. a system that enables drugs to be purchased electronically. SNOMED International does not advise implementers on this matter, but recommends that implementers, who are in any doubt, contact the trademark owner.

In general, implementers should make no greater use of a trademark than is necessary. For example, displaying a graphical mark (e.g., a logo) on a screen or in printed material should be avoided.

Questions, answers, and scores

Implementers should manage questions, answers, and scores in the same way as SNOMED International. When the incorporation of content from a clinical form or tool infringes on the copyright, the system the reproduces (by display or print) the content also usually infringes. This means that the license to incorporate content by SNOMED International should also cover the system implementer.

Preexisting terms

As noted above, terms in a clinical form may already exist within SNOMED CT, even though they have not been copied from the form. This is not copyright infringement by SNOMED International. If, however, a system implementer chooses to arrange a collection of these pre-existing terms in a way that reproduces all or a substantial part of a clinical form (e.g., by populating a drop-down box with all of the possible answers to a specific question on the form), that may infringe on the copyright.

A system may reproduce the structure and layout of a clinical form on a screen display or printed output (e.g., to make the system more accessible to users who are familiar with a paper-based form). This may infringe on the copyright, unless the structure or layout is very minimal (e.g., a bulleted list). An implementer who wishes to emulate the look and feel of a clinical form should seek a license from the owner.

System implementers may use the algorithm or logic inherent in a clinical form or tool (e.g. the method by which an overall score is calculated). For example, a clinical form may instruct the user to perform a mathematical operation on the individual answers to produce the overall score, and the same operation may be carried out by the system. The use of the algorithm or logic is an infringement. SNOMED International avoids such use and encourages system implementers to contact the owner to discuss possible infringement.

This Editorial Guide is used for Education Purposes Only. It is used in the Authoring Courses and Certifications. It is based on the January 2026 Editorial Guide.

For those concepts that describe a congenital anomaly that has been repaired and subsequently acquired an abnormality, follow the naming convention of |Acquired abnormality of X following repair of congenital X (disorder)|.

• For example,

  • 871598001 |Acquired abnormality of common arterial trunk following repair of truncus arteriosus (disorder)|

This Editorial Guide is used for Education Purposes Only. It is used in the Authoring Courses and Certifications. It is based on the January 2026 Editorial Guide.

Background

SNOMED CT is a comprehensive, international, logic-based reference terminology designed to represent clinically relevant information in a consistent, computable way. Originating from the union of NHS Clinical Terms Version 3 and SNOMED RT, it has evolved to support contemporary clinical practice and technological advances . The Editorial Guide exists to support the ongoing development and quality assurance of this terminology, ensuring content is modeled consistently and in alignment with best practices.

Content development is provided by expert clinicians driven by the requirements of user communities. This includes core content for use internationally and content relevant to national extensions for local implementation.

Its logic-based definitions represent terminological knowledge, or what is always true about the meaning of concepts. It consists of codes, that correspond to concepts, arranged in a polyhierarchical manner, as well as relationships between the concepts, which further define the meaning.

Description logic (DL) is the formal foundation of meaning in SNOMED CT. The way that concepts have been modeled in SNOMED CT permits them to be represented using description logic. A DL reasoner is used to classify SNOMED CT. The DL reasoner also helps test expressions for subsumption and equivalence.

The SNOMED CT Editorial Guide provides the rules, conventions, and principles required to model SNOMED CT concepts. It serves as the definitive reference for authoring and maintaining content in the International Release, while also supporting extension creators . The guide ensures that terminology is reliable, unambiguous, and interoperable for healthcare applications.

This guide covers the editorial policies for precoordinated content, meaning concepts and rules applicable to all precoordinated SNOMED CT content. Rules specific only to postcoordinated content are not included; these are managed separately through the MRCM () browser . It also provides information on concept modeling, naming conventions, inactivation, attributes, and rules for specific hierarchies.

Text that is protected by copyright will not be accepted for inclusion unless accompanied by a release from the copyright holder.

The primary audience of the Editorial Guide is SNOMED International editors responsible for maintaining the International Release. However, it is also relevant for extension developers, implementers, and others involved in clinical terminology management . For national or local extensions, the offers complementary guidance.

The Editorial Guide is a living document that is continually revised. The spreadsheet records changes via monthly tabs.

The Editorial Guide is maintained by SNOMED International, the organization responsible for the ongoing development and distribution of SNOMED CT. Users are encouraged to provide feedback or seek clarification by contacting SNOMED International at . Additional resources, licensing details, and membership information are available at .

This Editorial Guide is used for Education Purposes Only. It is used in the Authoring Courses and Certifications. It is based on the January 2026 Editorial Guide.

Fully specified names and preferred names should use proper names of digits of hand and foot. The names by order of digits can be added as optional synonyms. The order of fingers is different from the order of digits of hand because the thumb is not a finger in SNOMED CT. Therefore, the order of the finger should not be used to avoid potential confusion.

This Editorial Guide is used for Education Purposes Only. It is used in the Authoring Courses and Certifications. It is based on the January 2026 Editorial Guide.

All fully specified names (FSN) should be represented in US English. When there is a difference between the US and GB spelling, there should be US and General British (GB) preferred terms (PT) and/or synonyms (SYN).

• For example:

  • FSN: Benign tumor of endocrine pancreas (disorder)

This Editorial Guide is used for Education Purposes Only. It is used in the Authoring Courses and Certifications. It is based on the January 2026 Editorial Guide.

Both subchoroidal and suprachoroidal refer to the same potential anatomic space between the choroid and the sclera. The term lamina subchoroidea of choroid is the same as the lamina suprachoroidea.

There is not a vein actually named retinal vein. However, SNOMED CT has concepts with the phrase.

For example,