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 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 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:
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)