Plural of Appendix
“Appendix” has two current plurals with a clear sense preference. In anatomy, the ordinary plural is “appendixes.” In books and documents, “appendices” is the usual form, while “appendixes” remains accepted. The right editorial decision therefore starts with the meaning.
Both “appendixes” and “appendices” are accepted plurals of “appendix,” but meaning strongly affects preference. For the body part, “appendixes” is usual; for sections at the end of books or documents, “appendices” is usual, though “appendixes” is also accepted there.
Key details
Choose the right form
| Meaning / situation | Form / construction | Decision |
|---|---|---|
| body part | appendixes | Usual plural for the anatomical sense. |
| book/document section | appendices | Usual plural for the document sense. |
| book/document section with regular English plural | appendixes | Also accepted; follow style consistency. |
Quick tests
Plural-choice test
Does “appendix” mean the body part?
If yes: Use “appendixes” as the usual plural.
If no: For book/document sections, “appendices” is usual, while “appendixes” is also accepted.
Caveat: The two accepted forms have meaning-dependent preferences, so avoid a one-size-fits-all rule.
Examples
The surgeon examined two appendixes.
The body-part sense usually takes “appendixes.”
The report includes three appendices.
“Appendices” is usual for document sections.
The manual groups technical appendixes at the end.
“Appendixes” is also accepted for document sections, though “appendices” is usual.
Further guidance
Core difference
Use “appendixes” for anatomical appendixes. Use “appendices” as the usual plural for book/document sections, unless a style or source consistently uses “appendixes.”
Fast Test
Ask what the noun names: body part → “appendixes”; added book/document section → usually “appendices.”
Usage Boundary
Do not present either form as universally mandatory across both meanings.
Sources and evidence
Sources are shown with the role they play in this guide. Historical or style-sensitive claims are kept within the evidence boundary described above.
- APPENDIX | English meaning - Cambridge Dictionary (opens in a new tab)Cambridge University Press · Cambridge gives appendixes for the body-part sense and appendixes or appendices for the book/document sense, establishing a meaning-dependent plural boundary.
- appendix noun - Oxford Advanced Learner’s Dictionary (opens in a new tab)Oxford University Press · Oxford gives appendixes or appendices and says appendixes is usual for body parts while appendices is usual for book/document sections.