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 biliary calculi

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,

• 
• , has IS A 

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

For example,

• • Bilateral atrophy of testes (disorder)