> For the complete documentation index, see [llms.txt](https://docs.snomed.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.snomed.org/education/snomed-ct-education-editorial-guide/readme/authoring/general-naming-conventions/plurals.md).

# Plurals

<mark style="color:$danger;">**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.**</mark>

## Fully specified names (FSNs) <a href="#fully-specified-names-fsns" id="fully-specified-names-fsns"></a>

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

* For example:
  * |Disorder of lung (disorder)|, not |Disorder of lungs|
  * |Acute cholecystitis due to biliary calculus (disorder)|, not |Acute cholecystitis due to biliary calculi (disorder)

FSNs should not be plural unless the concept necessarily involves multiples.

## Unintended plurals <a href="#unintended-plurals" id="unintended-plurals"></a>

*Unintended plurals* might be incorrectly interpreted. An unintended plural is the use of a plural when, in fact, there is only one entity.

* Correct example:
  * *Multiple cranial nerve palsies*; the word *multiple* indicates that there can never be just one, so the plural *palsies* is correct
* Incorrect example:
  * *Trochlear lesion* versus *trochlear lesions;* users would use this concept to refer to a single trochlear lesion, thus the plural form would be incorrect

## Exceptions <a href="#exceptions" id="exceptions"></a>

Organizational nodes or grouper concepts may be plural.

* For example,
  * 234320004 | Procedures for splenic lesions (procedure)|
  * 194732001 | Diseases of mitral and aortic valves (disorder)|, has IS A 195002007 | Multiple valve disease (disorder)|

A concept that necessarily involves multiples should have a plural FSN.

* For example,
  * Bilateral atrophy of testes (disorder)

{% hint style="warning" %}
It is advisable to keep track of these exceptions in a separate subset or using a special term type, so that they can be excluded when the singular/plural distinction is important for mapping.
{% endhint %}

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