Both appendices and appendixes are correct plurals of appendix, but they are not used the same way. Appendices is the standard choice for the extra material at the end of a document, while appendixes is more common when talking about the body organ, especially in American medical writing.
Quick Answer
If you are writing a report, thesis, or book and adding supporting material at the end, use appendices. If you are writing about the body part that sometimes gets removed in surgery, appendixes shows up more often in clinical and everyday health writing, though appendices is still accepted there too.
| Situation | Preferred Form |
|---|---|
| Document sections (reports, books, papers) | Appendices |
| Anatomy (the organ) | Appendixes (also appendices) |
| Academic and formal writing | Appendices |
| Casual or medical American English | Appendixes |
Examples
- The thesis included three appendices with raw survey data.
- Surgeons removed one of the patient’s two vermiform appendixes in separate procedures years apart.
- Check Appendix B for the full source list.
- Doctors compared inflammation rates across several appendixes in a small case study.
Appendices vs Appendixes: The Core Meaning
1. In Writing
An appendix, in a written document, is a section placed after the main text that holds supporting material. This includes raw data, charts, glossaries, or source documents that would clutter the main argument if left inside it. When a document has more than one, most style guides call for appendices.
2. In Anatomy
The appendix is a small pouch attached to the large intestine. It has no confirmed critical function in humans, though some researchers link it to gut bacteria storage. When more than one appendix organ is discussed, such as in comparative case studies, writers often reach for appendixes instead of the Latin form.
Appendices vs Appendixes: The Real Difference
Both words trace back to the same Latin root, appendix, meaning something attached. The difference is not meaning. It is which plural pattern the word follows once it entered English, and which communities settled on which form over time.
Key point: Neither word is a typo or an error. They are competing plurals of the same singular noun, and usage has split by context rather than by correctness.
Grammar Rule Depth
Latin Origin Rule
Appendix comes from Latin, and many Latin nouns ending in -ix or -ex historically pluralize by swapping that ending for -ices. Index becomes indices, matrix becomes matrices, and appendix becomes appendices under this same pattern. This is the older, more formal route.
English Plural Rule
English also has a simpler habit: add -es to nouns ending in x. Box becomes boxes, fox becomes foxes, and under this logic appendix becomes appendixes. This form treats the word as a fully naturalized English noun rather than a borrowed Latin one.
Key insight: English rarely forces a single winner when two plural patterns compete. Formal registers tend to keep the Latin form, while everyday and clinical registers tend to regularize it. Appendix sits right at that fault line, which is why both spellings remain alive today.
The Origin of Appendix
The word entered English in the 1500s through Latin, where appendere meant to hang something onto. Writers first used it for an addition hung onto the end of a book or document. The anatomical sense came later, once physicians began naming the small organ for its position hanging off the intestine.
Why People Confuse Appendices and Appendixes
Multiple Correct Forms
Most English nouns have one clear plural, so seeing two accepted spellings for the same word throws people off. Writers assume one form must be wrong, when in fact style guides and dictionaries list both without flagging either as incorrect.
Academic vs General Usage
Academic writing leans hard toward appendices because that world already uses other Latin plurals like criteria and data. General and business writing has fewer of those habits, so the simpler -es plural feels more natural and appendixes slips in more easily.
Latin Influence
English absorbed thousands of Latin and Greek loanwords, and many kept irregular plurals long after the words became everyday vocabulary. Appendix is a mid-point case. It kept its Latin plural in formal writing but picked up a regular English plural everywhere else.
Which Spelling Should You Use
Academic and Professional Writing
Use appendices for theses, dissertations, business reports, legal filings, and published books. Style guides including APA and Chicago default to this form, and readers in those fields expect it. Straying from it can look like a small inconsistency in an otherwise polished document.
Business and General Writing
For internal memos, blog posts, emails, and general business writing, either form reads fine. Appendixes is perfectly acceptable here, and some readers find it easier to parse since it looks more obviously plural to a non-specialist eye.
Safe rule: When in doubt, match whichever form your document, company, or publication already uses elsewhere. Consistency inside one document matters more than picking the theoretically superior form.
Real World Usage of Appendices vs Appendixes
Academic Writing
Universities and academic publishers overwhelmingly print appendices in dissertations, journal articles, and textbooks. Citation manuals reinforce this by listing appendices as the standard term in their formatting guidance.
Business Reports
Corporate and government reports mostly follow the academic pattern and use appendices for supporting exhibits, financial tables, and technical annexes attached to a main report.
Books and Publications
Nonfiction books, style manuals, and reference works almost always print Appendices as the section header, even when the author’s everyday speech might lean toward the other form.
Appendices vs Appendixes in Everyday Examples
Emails
“I’ve attached the pricing sheets as appendices to this proposal” reads as professional and expected in a formal email chain.
Reports
“See Appendix 2 for methodology” is the standard phrasing across nearly every report format, academic or corporate.
Social Media
Casual posts about health, like discussing appendix surgery, more often use appendixes when referring to more than one case, since the tone is conversational rather than formal.
Formal Writing
Legal contracts, government filings, and technical manuals default to appendices almost without exception, treating it as house style regardless of author preference.
Common Mistakes with Appendices vs Appendixes
Mistake 1: Mixing Both Forms
Using appendices in one paragraph and appendixes in the next inside the same document breaks consistency. Pick one form per document and stay with it from the first mention to the last.
Mistake 2: Using the Informal Form in Academic Writing
Submitting a dissertation with appendixes instead of appendices will not usually get marked wrong, but it can read as slightly off in a field where Latin plurals are the norm. Follow your institution’s style guide first.
Mistake 3: Assuming One Is Wrong
Some writers correct appendixes to appendices as if fixing an error, even in casual or medical writing where appendixes is standard. Both forms appear in major dictionaries, so neither needs correcting on sight.
Appendices vs Appendixes in Different Contexts
Academic Context
Appendices dominates almost completely, reinforced by decades of style guide precedent in APA, MLA, and Chicago formatting.
Informal Context
Either form works, though appendixes often feels more natural in speech and casual text since it follows the pattern speakers already use for other English plurals.
Medical Context
American clinical writing and patient-facing health content frequently use appendixes when discussing more than one organ across cases or patients, while British medical writing leans slightly more toward appendices.
Related Words and Similar Plurals
Several other Latin-origin English words face the same split:
- Index: indices (formal, mathematical) or indexes (general, publishing)
- Matrix: matrices (formal, scientific) or matrixes (rare, informal)
- Vortex: vortices (formal) or vortexes (informal)
Appendix follows this same family pattern, splitting along formal versus general usage lines rather than right versus wrong.
Usage Trends
Corpus data on published English shows appendices holding a strong lead in books, academic journals, and news writing, largely because those genres skew formal. Appendixes shows up more in health articles, forums, and everyday web content where writers are not bound by academic style guides. Neither form is fading out, since both serve genuinely different registers.
Exercise 1: Choose the Correct Form
- The dissertation contained five ______ (appendices/appendixes) of raw data.
- Doctors reviewed scans of two patients’ ______ (appendices/appendixes) after surgery.
- Please refer to ______ (Appendix/Appendixes) C for the full budget.
Exercise 2: Correct the Sentence
Original: “The report has three appendixes, and appendix A lists all appendices sources.” Corrected: The report has three appendices, and Appendix A lists all sources.
FAQs
What is the difference between appendices and appendixes?
There is no difference in meaning. Appendices follows the Latin plural pattern and dominates formal writing, while appendixes follows the regular English plural pattern and appears more in casual or medical contexts.
Is it appendices or appendixes in a report?
Use appendices in reports. It is the standard form across business, academic, and government writing.
Do I say appendices or appendix?
Appendix is singular. Appendices (or appendixes) is plural. Use appendix when referring to just one section or organ.
What are appendixes?
Appendixes is an accepted plural of appendix, more common in American medical writing and casual text than in formal documents.
Final Thoughts
Appendices and appendixes are not a right versus wrong pair. They are two valid plurals that split along formal and informal lines, much like indices and indexes. Pick appendices for academic, business, and published writing, and let appendixes stand where casual or clinical American usage already favors it.
The only real mistake is switching between the two inside the same document. Choose one form early, check your style guide if you have one, and stay consistent from the first appendix mention to the last. That consistency matters more than which form you pick.