Synonym

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 SNOMED CT, a synonym (SYN) is a description that is an acceptable way to express the meaning of a concept in a particular language or dialect; it is a word or phrase, other than the FSN, that represents a concept. Unlike FSNs, synonyms are not required to be unique.

Each concept may have one or more synonyms.

For example,

• US English synonyms for 22298006 | Myocardial infarction (disorder)| are:

  • Myocardial infarction

  • Cardiac infarction

  • Heart attack

  • Infarction of heart

  • MI - myocardial infarction

  • Myocardial infarct

A synonym may not change to, i.e. replace, an existing FSN.

When a synonym is more specific than the FSN, it does not have the same meaning, and should be inactivated. The description inactivation value of 723278000 |Not semantically equivalent component (foundation metadata concept)| is used.

For example,

• FSN: Removal of device (procedure)

• SYN: Removal of prosthetic device (procedure)

Removal of prosthetic device has a more specific meaning than Removal of device ; therefore, the synonym Removal of prosthetic device should be inactivated from the concept.

When a synonym is more general than the FSN, and there is no context in which it has the same meaning as the FSN, the synonym should be inactivated. The description inactivation value of 723278000 |Not semantically equivalent component (foundation metadata concept)| is used.

For example,

• FSN: Sprain (morphologic abnormality)

• SYN: Joint injury - more general meaning than the FSN

Joint injury has a more general meaning than Sprain ; therefore, the synonym Joint injury should be inactivated from the concept.

Two active descriptions in the same hierarchy should not share the same term unless the language is different.

Where two or more concepts have the same description(s), both concepts must be checked to determine whether the concepts are in fact duplicates. If the concepts are duplicates, one concept is inactivated with the inactivation reason of SAME_AS and historical association to the other concept.

A description with a single meaning may be erroneously associated with more than one concept. If the concepts are not duplicates, the description should be retained with only one of the concepts and inactivated on the other(s).

Some descriptions have more than one meaning when this is considered in conjunction with the hierarchy the concept is situated in. The purpose of the semantic tag is to disambiguate concepts that have the same commonly used word or phrase. Therefore, there are circumstances where the same description can be appropriate, either as the preferred term or synonym, for concepts in different hierarchies.

The most common example of this is clinical finding/disorder/morphologic abnormality hierarchies where the disorder and the associated morphology may use the same descriptions.

For example,

• Preferred term - Intravascular large B-cell lymphoma

• Preferred term - Intravascular large B-cell lymphoma

The morphologic abnormality concept is used as the value for associated morphology to sufficiently define the disorder concept.

Furthermore, the same description might refer to an action for a procedure, a morphologic abnormality to describe an abnormal body structure, or a clinical finding/disorder describing a normal/abnormal observation or clinical state, judgement, or assessment.

For example,

Abrasion is a description for:

• Synonym Abrasion

• Preferred term Abrasion

• Preferred term Abrasion

Further examples below illustrate where a duplicate description may be published on separate concepts in different hierarchies, and these are clinically accurate and required to present clinically relevant information.

• Synonym - 24 hour urine volume

• Synonym - 24 hour urine volume

Preferred term - Acid fast stain

• Synonym - Acid fast stain

• Preferred term - Acriflavine stain

• Synonym - Acriflavine stain

• Preferred term - Activated coagulation factor

• Preferred term - Activated coagulation factor

• Preferred term - Ankle brachial pressure index

• Preferred term - Ankle brachial pressure index

Where the case significance is deliberately different for descriptions across one or more concept(s), these differences may be included for clinical relevance and are not duplicate descriptions.

For example,

• Synonym - Alpha-N-acetylglucosaminidase deficiency [cI]

• Synonym - alpha-N-acetylglucosaminidase deficiency [CS]

When creating a duplicate description for concepts in two separate hierarchies, it is important to check that the descriptions are truly synonymous with the FSN. There may be cases where an additional word(s) may remove the duplication and reduce the risk of adding a broader or narrower description than the FSN. Where it is not possible to do this, it is acceptable for these duplicate descriptions to coexist across different hierarchies.