Plurals
Fully specified names (FSNs)
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
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
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)
For organism groupers, plural common names may be appropriate when supported by the reference. Pluralization is not applied automatically. Where singular and plural forms distinguish a subtype (e.g. species) from its grouper (e.g. genus), the form supported by the reference is retained.
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.