If you are writing an academic paper, a medical report, or even a business proposal, you will likely need to refer to the supplementary material at the end of a document. The most common mistake with the plural of “appendix” is using the wrong form for your context: many writers use “appendices” when they mean “appendixes,” or vice versa. The correct choice depends on whether you are writing in a formal academic or scientific field (where “appendices” is standard) or in a general, medical, or informal context (where “appendixes” is perfectly acceptable). This guide will help you choose the right form every time.
Quick Answer: Appendices vs. Appendixes
Both “appendices” and “appendixes” are correct plural forms of “appendix.” The difference is one of usage and tone:
- Appendices – The traditional Latin plural. Preferred in formal academic writing, research papers, and legal documents.
- Appendixes – The English plural. Common in general writing, medical contexts (referring to the human body), and everyday conversation.
If you are writing a thesis or a formal report, use appendices. If you are talking about a medical condition or writing an informal email, use appendixes.
Understanding the Two Plurals
The word “appendix” comes from Latin, where it belongs to a group of nouns that end in “-ix” or “-ex” and form their plural with “-ices.” This is why we have “appendices” (like “indices” and “matrices”). Over time, English speakers began adding the regular “-es” ending, creating “appendixes.” Both forms are now standard, but they have settled into different roles.
When to Use “Appendices”
Use “appendices” when you are referring to supplementary sections at the end of a book, report, or academic document. This is the preferred form in most style guides, including APA, MLA, and Chicago Manual of Style.
Formal tone: “Appendices” sounds more scholarly and precise. It is the expected form in academic journals, dissertations, and official publications.
Example in a research paper: “The full survey data are available in the appendices.”
Example in an email to a professor: “I have attached the appendices for your review.”
When to Use “Appendixes”
Use “appendixes” in two main situations: when talking about the human body (the vermiform appendix) and in general, less formal writing.
Medical context: “Several patients had inflamed appendixes.”
Informal or general context: “The report has three appendixes with charts.”
Conversation: “I checked the appendixes at the back of the book.”
Comparison Table: Appendices vs. Appendixes
| Feature | Appendices | Appendixes |
|---|---|---|
| Origin | Latin plural | English plural |
| Formality | Formal, academic, legal | General, medical, informal |
| Common use | Research papers, books, theses | Medical reports, emails, conversation |
| Style guide preference | APA, MLA, Chicago | No strong preference; acceptable in all |
| Example sentence | “Refer to the appendices for raw data.” | “Two patients had their appendixes removed.” |
Natural Examples
Here are real-world examples showing how both forms are used in different situations.
Academic Writing (Formal)
- “The appendices contain the interview transcripts and coding tables.”
- “Please see Appendices A through C for the complete methodology.”
- “All supplementary materials are listed in the appendices.”
Medical Writing (Clinical)
- “The surgeon removed both appendixes during the procedure.”
- “In rare cases, patients can have two appendixes.”
- “The CT scan showed inflamed appendixes in three subjects.”
General / Business Writing
- “The contract appendixes include the payment schedule.”
- “I have added two appendixes to the proposal.”
- “Check the appendixes for the full list of references.”
Everyday Conversation
- “I looked at the appendixes in the textbook, but they weren’t helpful.”
- “How many appendixes does the manual have?”
- “The doctor said my appendixes were fine.”
Common Mistakes
Even experienced writers make errors with this word. Here are the most frequent mistakes and how to avoid them.
Mistake 1: Using “Appendices” for Body Parts
Incorrect: “The patient had two appendices.”
Correct: “The patient had two appendixes.”
When referring to the human organ, always use “appendixes.” Using “appendices” in a medical context sounds unnatural and may confuse readers.
Mistake 2: Using “Appendixes” in Formal Academic Papers
Incorrect: “The appendixes are located after the bibliography.”
Correct: “The appendices are located after the bibliography.”
In academic writing, “appendices” is the standard form. Using “appendixes” may make your work look less professional.
Mistake 3: Mixing Forms in the Same Document
Incorrect: “See Appendix A. The other appendixes are listed below.”
Correct: “See Appendix A. The other appendices are listed below.”
Choose one form and stick with it throughout your document. Consistency is key.
Mistake 4: Using “Appendices” as a Singular
Incorrect: “This appendices contains the data.”
Correct: “This appendix contains the data.” or “These appendices contain the data.”
“Appendices” is always plural. The singular form is “appendix.”
Better Alternatives and When to Use Them
Sometimes, you can avoid the confusion entirely by using alternative words. Here are some options:
- Supplement / Supplements – Use in general writing when you want a neutral term. “The report includes several supplements.”
- Addendum / Addenda – Use for a single addition or multiple additions to a document. “The addenda clarify the contract terms.”
- Annex / Annexes – Common in legal and international documents. “The annexes contain the treaty details.”
- Supporting materials – A clear, plain-English option. “The supporting materials are in the back.”
When you are unsure, “supplements” or “supporting materials” are safe choices that work in almost any context.
Mini Practice: Test Your Knowledge
Choose the correct plural form for each sentence. Answers are below.
- The thesis has three (appendices / appendixes) with survey results.
- The doctor said both (appendices / appendixes) were healthy.
- Please refer to the (appendices / appendixes) for the full dataset.
- I added two (appendices / appendixes) to the end of the manual.
Answers:
- Appendices – Formal academic context.
- Appendixes – Medical context, referring to body parts.
- Appendices – Formal research context.
- Appendixes – General, informal writing.
Frequently Asked Questions
1. Is “appendices” the only correct plural?
No. Both “appendices” and “appendixes” are correct. “Appendices” is the traditional Latin plural and is preferred in formal academic writing. “Appendixes” is the regular English plural and is common in medical and general contexts.
2. Which plural should I use in a business report?
For most business reports, either form is acceptable. If your company follows a specific style guide, check that first. Otherwise, “appendices” sounds more formal and is often the safer choice for professional documents.
3. Can I use “appendix” as a plural?
No. “Appendix” is singular. The plural forms are “appendices” or “appendixes.” Using “appendix” for multiple items is incorrect.
4. What about “appendices” in medical writing?
In medical writing about the human body, “appendixes” is the standard term. However, if you are writing a medical research paper that includes supplementary materials, you would use “appendices” for those sections. The context determines the correct form.
Final Tip
When in doubt, think about your audience. If you are writing for a professor, journal editor, or lawyer, choose “appendices.” If you are writing for a general reader, a patient, or a colleague in an email, “appendixes” is perfectly fine. The most important rule is to be consistent throughout your document.
For more help with tricky plural forms, explore our guides on Confusing Plurals or check our Common Plural Forms section. If you have questions about singular or plural usage, visit our Singular or Plural Checks page. For detailed spelling rules, see our Plural Spelling Rules category. You can also read our FAQ for more answers.
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