Both “appendices” and “appendixes” are correct plurals of “appendix.” Use “appendices” for documents and books, and “appendixes” for the body organ, especially in medical contexts.
The Word That Splits Writers and Doctors
A writer friend once argued with her editor for twenty minutes over a single letter. She wrote “appendixes” at the end of her report. Her editor circled it and wrote “appendices” in red.
Both of them were right, and neither of them knew it.
This is one of those rare English words with two accepted plural forms, and each one leans toward a different world. One belongs in libraries and legal documents. The other belongs in hospitals.
This guide settles the debate once and for all, so you always pick the version that fits your context.
Appendices or Appendixes: Quick Answer
“Appendices” is the plural most people use for supplementary sections at the end of books, reports, or contracts. Example: The report included three appendices with raw data.
“Appendixes” is more common in medical writing, referring to the small organ attached to the large intestine. Example: Surgeons removed both patients’ appendixes during separate operations.
Either form is grammatically correct in general use, but the context shapes the expected choice.
The Origin of Appendix, Appendices, and Appendixes
“Appendix” comes from Latin “appendere,” meaning “to hang onto.” The original Latin plural was “appendices,” following standard Latin pluralization rules.
As English absorbed the word, it also developed its own native plural pattern by simply adding “es,” giving us “appendixes.”
Over time, “appendices” became strongly associated with academic and publishing contexts, since Latin plurals often survive longest in formal writing. “Appendixes” took over in everyday and medical English, where regular English pluralization feels more natural.
Appendices vs Appendixes: Key Differences and Uses
| Term | Meaning | When to Use | Region/Context |
|---|---|---|---|
| Appendices | Sections at the end of a document | Books, reports, legal writing, academic papers | Preferred in publishing and formal writing worldwide |
| Appendixes | The bodily organ, plural | Medical and biological writing | Preferred in healthcare and everyday speech |
Examples in context:
Appendices (document use): The thesis contained five appendices with survey results. Appendixes (medical use): Both twins had their appendixes removed within a year of each other. Appendices (document use): Check appendix B in the appendices section for full data. Appendixes (medical use): Inflamed appendixes require prompt surgical attention.
Which Version Should You Use?
For academic writing, business reports, or legal documents, use appendices because it matches long standing publishing conventions.
Then, For medical writing, healthcare communication, or casual speech about the organ, use appendixes because it feels more natural and is widely accepted in that field.
And For general neutral use, when you are unsure of your audience, appendices remains the safer, more formal choice.
Common Mistakes with Appendices and Appendixes
Mistake: Using “appendices” when referring to the body organ in casual conversation. Correction: Use “appendixes” for the organ in everyday and medical speech. Why it happens: writers assume one plural fits every context, without noticing the field specific convention.
Mistake: Using “appendixes” in a formal academic report. Correction: Use “appendices” in academic and publishing contexts. Why it happens: the regular English plural feels more intuitive, so it slips in even in formal writing.
Mistake: Mixing both spellings within the same document. Correction: Pick one form and stay consistent throughout your writing. Why it happens: writers switch unconsciously when they are unsure which is correct.
Mistake: Assuming one version is simply wrong. Correction: Both are accepted, so check your context instead of memorizing a single rule. Why it happens: many grammar guides oversimplify this pair into a strict right or wrong choice.
Appendices and Appendixes in Real World Examples
In a professional email: “Please find the supporting data in the appendices attached to this report.”
In a news headline: “Surgeons Warn Ruptured Appendixes Are Rising Among Teenagers”
Then in a social media post: “Just finished writing my thesis, and the appendices alone are twenty pages long.”
And In a formal document: “See appendixes A through C for full clinical trial results on appendicitis cases.”
Appendices and Appendixes: Data, Trends and Usage
Searches for “appendices or appendixes” come mostly from students, writers, and editors preparing formal documents who want to confirm the correct plural.
Medical students and healthcare writers also search this term, usually when writing about the organ rather than a document section.
This is a purely informational search, focused on grammar clarity rather than any product or service.
It matters now because more people write reports and academic papers using online tools, and spell checkers often flag one version as incorrect even though both are valid.
Appendices vs Appendixes: Standalone Comparison Table
| Term/Variant | Meaning | Region/Context | Best Used When |
|---|---|---|---|
| Appendices | Plural of document supplement | Academic, legal, business writing | Referring to sections at the end of a document |
| Appendixes | Plural of bodily organ | Medical and everyday speech | Referring to the physical organ |
Frequently Asked Questions
Q: What does “appendices” mean? A: “Appendices” refers to the supplementary sections placed at the end of a book, report, or document, containing extra data or references.
Q: How do you use “appendixes” correctly? A: Use “appendixes” as the plural for the bodily organ, especially in medical or everyday conversational contexts.
Q: Appendices vs appendixes, what’s the actual difference? A: Both are correct plurals of “appendix,” but “appendices” fits documents, while “appendixes” fits the human organ.
Q: Is “appendixes” acceptable in formal writing? A: Yes, but mainly in medical or scientific formal writing. For general academic and business writing, “appendices” remains the stronger choice.
Q: Which version is correct, “appendices” or “appendixes,” in a legal contract? A: “Appendices” is the standard and expected form in legal and business documents.
Q: Where does the word “appendix” come from? A: It comes from the Latin word “appendere,” meaning “to hang onto,” describing something attached as an extra part.
Q: Can both plurals be used in the same document? A: Technically yes, but it looks inconsistent. Pick one form and use it throughout your entire document.
Final Takeaways
Here is the whole rule in one line: appendices for documents, appendixes for the organ.
Both spellings are correct, so context decides your choice, not a strict grammar rule.
Staying consistent within one document matters more than picking the “perfect” version.
Bookmark this guide so you never second guess appendices or appendixes again, and share it with anyone writing a report or a medical note today.
Read More: Separate or Seperate: The Correct Spelling Explained
I’m Zain. I got interested in commonly confused words while helping non-native English speakers prep for writing exams, where a single misused word could cost real marks. That experience shaped how I write now: I try to explain not just which spelling is correct, but why the confusion exists in the first place, since understanding the reason is what actually makes it stick.
