Ever stared at the word appendix and wondered: Is the plural appendixes or appendices? You’re not alone. This is one of those English quirks that keeps writers and editors second-guessing themselves. The good news? Both forms exis but they aren’t always interchangeable. Let’s break it down in plain English so you’ll never hesitate again.
What Is an Appendix? (Quick Refresher)
Before we jump into plurals, let’s make sure we’re on the same page about the appendix definition. The word appendix has two main meanings:
- Anatomy – A small, tube-like organ attached to your large intestine. (Yes, the one that sometimes gets inflamed appendicitis.)
- Books and Documents – A section added at the end of a book or report, often for references, charts, or supporting details.
Example:
“Please check the appendix for the full data tables.”
So far, so good? Great! Now, the tricky part: the plural of appendix.
Plural of Appendix: Appendices or Appendixes?
Here’s where the confusion begins. Both appendices and appendixes are correct. But usage depends on context and sometimes even style preference.
- Appendices → Follows the Latin irregular plural rule, changing -ix to -ices.
- Appendixes → Regularized plural, adding -es like most English nouns.
So which one should you use? Let’s make it crystal clear.
Grammar Tip for Appendices vs Appendixes
- If you’re talking about books, reports, or documents, appendices is the preferred and more formal plural.
- If you’re talking about anatomy (body parts), appendixes is the usual choice, especially in medical contexts.
- Both forms are technically acceptable in general English, but style guides and context matter.
Why Two Plurals? (Blame Latin)
The word appendix came from Latin, and Latin words often bring their plural baggage with them. Like:
- matrix → matrices (or matrixes)
- index → indices (or indexes)
- codex → codices (or codexes)
These are irregular plural nouns. English borrowed the words and their plural rules but over time, simpler English-style plurals emerged. That’s why we have appendices (Latin style) and appendixes (English style).
Clear Rules & Patterns
Here’s a quick rulebook:
- For documents/books → Use appendices (sounds more academic and formal).
- For anatomy → Use appendixes (common in medical usage).
- In casual or non-technical contexts → Either is fine, but appendices looks more polished.
✅ Bulleted Rules with Do’s and Don’ts
- ✅ Do use appendices in research papers and professional writing.
- ✅ Do use appendixes when referring to the organ.
- ❌ Don’t mix them randomly in the same document.
- ✅ Do check your organization’s style guide (APA, MLA, Chicago) if you’re writing academically.
Multiple Example Sentences
- The report contains three appendices covering financial data, references, and case studies.
- Doctors examined two inflamed appendixes during surgery.
- I’ve attached several appendices for your review.
- The appendices provide additional research not included in the main text.
Scenario Examples (Emails & Professional Use)
Example 1: Business Email
Subject: Updated Report with Appendices
Hi James,
Please review the updated report. I’ve included two appendices: one with the market analysis and another with survey results.
Let me know if you need any additional details.
Best,
Karen
Example 2: Medical Report
Subject: Patient Case Summary
Dr. Miller,
The surgical team successfully removed two inflamed appendixes. Lab results are pending.
Regards,
Dr. Allen
Example 3: Academic Paper Note
“For full references and supplementary charts, see Appendices A and B at the end of this document.”
Common Mistakes & Fixes
- ❌ “The report has two appendixes for references.”
✔ Fix: “The report has two appendices for references.” - ❌ “The patient had two inflamed appendices.”
✔ Fix: “The patient had two inflamed appendixes.”
Quick Reference Table
| Word | Correct Plural | Usage |
|---|---|---|
| Appendix | Appendices | Books, documents |
| Appendix | Appendixes | Anatomy (body organ) |
Related Grammar Patterns
Words ending in -ix often have two plural forms:
- Index → indices / indexes
- Matrix → matrices / matrixes
- Codex → codices / codexes
Appendix fits this pattern. This is why both appendices and appendixes exist.
How to Remember the Difference
Think of it like this:
- Documents → appendices (formal, scholarly)
- Body parts → appendixes (medical context)
A quick mental hack: “Docs like ice (appendices), doctors like exes (appendixes).”
Before/After Examples in Everyday & Formal Contexts
Before:
“See the data in the appendix section.”
After:
“See the data in the appendices for complete analysis.”
Before:
“He had pain in his appendix, and doctors removed two appendices.”
After:
“He had pain in his appendix, and doctors removed two appendixes.”
Final Takeaways
- The plural of appendix can be appendices or appendixes, and both are correct.
- Use appendices for books, reports, and documents.
- Use appendixes for anatomy and medical contexts.
- Always consider context, style, and clarity.
