Common Mistakes with the Plural of Appendix

If you are writing a business report, a medical document, or even an email about a book, you may need the plural of appendix. The most common mistake is choosing between appendices and appendixes without knowing which one fits your context. Both forms are correct, but they are used in different fields and tones. Appendices is the standard choice in academic and formal writing, especially in books, research papers, and legal documents. Appendixes is more common in general business writing, medical notes, and everyday conversation. The key is to match the form to your audience and purpose.

Quick Answer

Use appendices for formal, academic, or legal contexts (e.g., a book, a thesis, a contract). Use appendixes for general business, medical, or informal writing (e.g., a report, a patient file, an email). Both are correct, but mixing them in the wrong setting can confuse readers.

Understanding the Two Plurals

The word appendix comes from Latin, and like many Latin words, it has two accepted plural forms. The Latin-based plural is appendices, and the English-based plural is appendixes. Neither is wrong, but usage has split over time.

When to Use Appendices

Appendices is the preferred form in formal writing. You will see it in:

• Academic papers and theses
• Published books (non-fiction and reference)
• Legal documents and contracts
• Technical manuals and standards

If you are writing a research proposal, a dissertation, or a formal business report that will be reviewed by senior management or external auditors, choose appendices. It signals that you are following standard academic or professional conventions.

When to Use Appendixes

Appendixes is the more natural English plural. It is common in:

• Internal business memos and emails
• Medical records and patient notes
• Everyday conversation and informal writing
• Software documentation and user guides

If you are writing a quick email to a colleague or updating a patient chart, appendixes sounds more natural and less stiff.

Comparison Table

Natural Examples

Here are real-world examples showing how each form is used in different situations.

Formal / Academic

• "The appendices to the report include survey results and interview transcripts."
• "All appendices must be numbered and listed in the table of contents."
• "The judge referred to the appendices in the court filing."

Informal / Business / Medical

• "I added the appendixes to the shared drive for the team."
• "The doctor noted that both appendixes were healthy."
• "Can you check the appendixes in the user guide before we publish?"

Common Mistakes

Even experienced writers make these errors. Here are the most frequent ones.

Mistake 1: Using Appendices in Casual Writing

Writing "Please see the appendices for the budget" in a quick email to a coworker can sound overly formal or pretentious. In internal communication, appendixes is more appropriate.

Mistake 2: Using Appendixes in Formal Documents

Submitting a thesis or a legal brief with "appendixes" may be seen as a lack of attention to style. Most style guides for academic writing require appendices.

Mistake 3: Mixing Both Forms in the Same Document

Do not write "See appendixes A and B" in one paragraph and "the appendices contain data" in another. Pick one form and use it consistently throughout the document.

Mistake 4: Confusing Appendix with Appendage

Some people mistakenly use appendage as a plural. Appendage means a body part that sticks out (like an arm or a tail). It is not a plural of appendix.

Better Alternatives

If you are unsure which form to use, or if you want to avoid the issue entirely, consider these alternatives.

• Supplement – Use for additional material in a report or book. "See the supplement for details."
• Addendum – Use for a single addition to a contract or document. "The addendum clarifies the payment terms."
• Attachment – Use for files sent with an email. "I have attached the budget spreadsheet."
• Annex – Use in formal or international documents. "The annex contains the full list of participants."

These words can help you avoid the appendix plural dilemma altogether, especially in business writing.

Mini Practice Section

Test your understanding with these four questions. Choose the correct form for each sentence.

Question 1

You are writing a formal research paper. Which sentence is correct?

A) The appendixes are located at the end of the document.
B) The appendices are located at the end of the document.

Answer: B) The appendices are located at the end of the document. In academic writing, appendices is the standard form.

Question 2

You are sending a quick email to a colleague about a project update. Which sentence sounds natural?

A) Please review the appendices before the meeting.
B) Please review the appendixes before the meeting.

Answer: B) Please review the appendixes before the meeting. In informal email, appendixes is more natural.

Question 3

You are editing a legal contract. Which form should you use?

A) Appendices
B) Appendixes

Answer: A) Appendices. Legal documents follow formal conventions.

Question 4

A doctor writes a note about a patient who had two appendixes removed. Is this correct?

A) Yes
B) No

Answer: A) Yes. In medical writing, appendixes is commonly used and accepted.

FAQ Section

1. Is it ever wrong to use appendices?

No, appendices is never grammatically wrong. However, it can sound too formal in casual or medical contexts. If you are writing an internal email or a patient note, appendixes is a better fit.

2. Can I use both forms in the same document?

It is best to avoid mixing them. Choose one form and use it consistently. Mixing them can confuse readers and make your writing look careless.

3. Which form do style guides recommend?

Most style guides, including APA, MLA, and Chicago, recommend appendices for academic and formal writing. For general business writing, there is no strict rule, but appendixes is more common in everyday use.

4. Does the meaning change between appendices and appendixes?

No, the meaning is the same. Both refer to additional material at the end of a document or to the small organ attached to the large intestine. The difference is only in formality and context.

Final Note

Choosing between appendices and appendixes is not about right or wrong. It is about matching your language to your audience. In formal documents, use appendices. In everyday business writing, medical notes, or emails, use appendixes. Consistency is more important than the form you choose. For more help with confusing plurals, visit our Confusing Plurals section or explore Common Plural Forms for other tricky words.