Appendices or Appendixes? Meaning and Usage in 2026

Ever finished writing a report, thesis, or business document, gotten to that final “extra stuff” section, and suddenly frozen? You type “appendix,” hit the plural button in your brain, and… nothing. Is it appendices? Is it appendixes? Did autocorrect just make one of them up? 🤔

You’re not alone. This is one of the most common English usage mix-ups for students, writers, and even native speakers. The confusion mostly comes from the fact that “appendix” has two correct plurals  and each one tends to show up in a different context.

Let’s clear this up once and for all, in plain, friendly English. No boring grammar textbook vibes, promise. 😊

Quick Answer ⚡

Both “appendices” and “appendixes” are correct plurals of “appendix.” Use appendices for the extra sections at the end of a document (formal/academic writing), and appendixes for the anatomical body part (informal/general writing)  though in everyday use, both are increasingly interchangeable.

Now let’s dig into the why behind this, because understanding it will make the rule stick forever. 🧠

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What Does “Appendix” Actually Mean?

Before we tackle the plural forms, let’s quickly define the singular word, since it has two completely different meanings:

1. A supplementary section at the end of a book, report, thesis, or document that contains extra information  like data tables, charts, references, or raw research.Copy
2. A small, tube-shaped organ attached to the large intestine in the human body (yes, the one people get removed in surgery  an appendectomy).Copy

Same word, totally different worlds. And that’s actually the key to remembering which plural to use. ✅

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Appendices vs. Appendixes: The Core Difference

Here’s the simplest way to think about it:

• Appendices → the classic, Latin-rooted plural. Common in academic, legal, technical, and formal writing for the “extra info” sections of a document.Copy
• Appendixes → the modern, English-style plural (just add “-es”). More common when referring to the body organ, and also acceptable for documents in casual writing.Copy

Examples in a Sentence

Using “Appendices” (documents/reports):

• The appendices at the back of the report include all the survey data. 📊Copy
• Please review Appendices A through D before the meeting.Copy
• The thesis had five appendices, including interview transcripts.Copy

Using “Appendixes” (body organ, or informal document reference):

• Doctors rarely see patients with two functioning appendixes  everyone has just one! 🏥Copy
• Some style guides now accept appendixes for the document sections too.Copy
• The medical textbook explained how appendixes can become inflamed.Copy

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Comparison Table: Appendices vs. Appendixes

Feature	Appendices	Appendixes
Origin	Latin plural form	Modern English plural (add “-es”)
Common Context	Academic papers, legal documents, business reports	Medical/anatomical references, casual writing
Formality Level	Formal, traditional	Slightly informal, modern
Example	“See Appendices B and C for full data.”	“The surgeon removed one of the two appendixes.”
Preferred By	Style guides like APA, MLA (for documents)	General/medical writing
Can They Overlap?	Yes  some guides accept either for documents	Rarely used for documents in strict academic writing

💡 Bottom line: When in doubt, “appendices” is the safer choice for anything document-related, especially in academic or professional settings.

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British English vs. American English 🇬🇧🇺🇸

This is where things get slightly more interesting. Here’s a general trend (not a hard rule):

• British English tends to lean toward “appendices” for both meanings  documents and the body part.Copy
• American English is a bit more flexible and often uses “appendixes” for the medical/anatomical meaning, while still preferring “appendices” for formal documents.Copy

Region	Preferred Plural (Documents)	Preferred Plural (Body Organ)
British English	Appendices	Appendices (sometimes Appendixes)
American English	Appendices	Appendixes

📝 Usage note: Dictionaries like Merriam-Webster and Oxford list both forms as correct, so you won’t technically be “wrong” either way  but consistency matters more than which one you pick.

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Common Mistakes to Avoid 🚫

Here are the slip-ups people make most often:

1. Mixing both forms in the same document. If you use “appendices” on page 3, don’t switch to “appendixes” on page 10. Pick one and stick with it  consistency is a golden rule in correct spelling and formatting.Copy
2. Using “appendix’s” as a plural. That apostrophe makes it possessive, not plural! ❌ “The appendix’s are attached” is incorrect.Copy
3. Overcorrecting in casual writing. You don’t need to say “appendices” when texting a friend about their surgery  “appendixes” (or just “appendix,” referring to the organ in general) sounds more natural.Copy
4. Forgetting capitalization when referencing specific ones. “See Appendix A” (capitalized, since it’s a specific title) vs. “check the appendices” (lowercase, general reference).Copy

Memory Trick / Mnemonic 🧠✨

Here’s an easy way to remember which one goes where:

“Appendi-CES for the PAGES. Appendi-XES for the eXtra organ.”

• CES rhymes with pages (documents 📄) → use Appendices.Copy
• XES sounds like “x-ray” (the organ, medical stuff 🩻) → use Appendixes.Copy

Say that out loud a couple of times  it really sticks!

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Real-Life Examples 🌍

Let’s see how this plays out in different everyday situations:

📧 In an Email

“Hi Sarah, I’ve attached the report  please check Appendices 1 and 2 for the full budget breakdown before Thursday’s call.”

📱 On Social Media

“Just had my appendix out last week 😩 apparently some people are born with weird extra tissue near their appendixes?? TIL”

📰 In the News

“Researchers found that human appendixes may play a bigger role in gut health than previously thought, according to a new study.”

🎓 In Academic Writing

“All raw data, including survey results and interview transcripts, can be found in Appendices C through F of this dissertation.”

💬 In Everyday Speech

“Can you send me the file with all the extra appendix pages? I think there were like four appendices in that document.”

Notice how “appendices” dominates in formal writing, while “appendixes” pops up more in casual, spoken, or medical contexts.

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Why Does English Have Two Plurals Anyway? 🤷‍♀️

This happens because “appendix” comes from Latin, and Latin-based words in English sometimes keep their original plural form (like cactus → cacti, fungus → fungi) while also picking up a regular English plural over time (cactus → cactuses, fungus → funguses).

Other words with this same “double plural” situation include:

• Index → indices / indexesCopy
• Formula → formulae / formulasCopy
• Syllabus → syllabi / syllabusesCopy

So if you’ve ever wondered why “indexes” and “indices” both exist too  same story! This is a great grammar tips nugget to keep in your back pocket for other tricky plurals.

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FAQs: People Also Ask 🙋

1. Is “appendices” or “appendixes” more correct?

Both are grammatically correct. “Appendices” is more traditional and preferred in academic/formal writing, while “appendixes” is common in casual or medical contexts.

2. What is the plural of appendix in medical terms?

In medical writing, “appendixes” is often used, though “appendices” is also acceptable in more formal or British contexts.

3. Can I use “appendices” and “appendixes” interchangeably?

Yes, in most everyday situations you can  but for consistency, pick one form and use it throughout your entire document.

4. Why does “appendix” have two plural forms?

Because it’s a Latin-origin word. English often keeps the original Latin plural (“appendices”) alongside a newer, regularized English plural (“appendixes”).

5. Which plural should I use in academic writing?

Always go with “appendices”  it’s the standard in APA, MLA, and Chicago style guides for document sections.

6. Is “appendix’s” a correct plural?

No. “Appendix’s” is possessive (showing ownership), not plural. The correct plurals are “appendices” or “appendixes.”

7. Do British and American English differ on this word?

Slightly. British English tends to favor “appendices” more broadly, while American English commonly uses “appendixes” for the anatomical meaning.

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Final Takeaway

In conclusion, appendices and appendixes are both correct plural forms of appendix. The word appendices is more traditional and is especially common in academic, medical, and formal writing. Appendixes is also grammatically correct and may sound more natural in general English. Your choice can depend on your audience, writing style, and regional preference. The important thing is to use one form consistently throughout your document.

You are writing a research paper, report, book, or other formal content, both forms are acceptable. Understanding this small difference helps you write with greater confidence and avoid unnecessary confusion when referring to multiple appendices or appendixes.