Is Appendix Singular or Plural?

The word appendix is singular. It refers to one item, whether you are talking about the organ in the human body or a section at the end of a book or document. The plural form is appendices (most common in academic and medical writing) or appendixes (acceptable in general English).

Quick Answer

Appendix is singular. Use appendices for formal, medical, or academic contexts. Use appendixes for everyday writing or informal conversation. Both are correct plurals, but the choice depends on your audience and tone.

Understanding the Singular Form

When you say appendix, you are talking about one thing. For example:

• The surgeon removed my appendix last night. (medical context)
• Please check the appendix at the back of the report. (document context)

In both cases, the word is singular. The confusion often comes from the fact that appendix has two accepted plural forms, which can make learners unsure whether the base word is singular or plural.

Which Plural Should You Use?

The table below shows the difference between the two plural forms and when to use each.

Both forms are grammatically correct. The choice is about tone and field. In medical writing, appendices is the standard. In a business email, appendixes sounds more natural and less stiff.

Natural Examples

Here are examples showing how the singular and plural forms work in real sentences.

Singular (Appendix)

• The doctor said my appendix is healthy.
• You will find the map in the appendix of the guide.
• One appendix is enough for this short report.

Plural (Appendices)

• The appendices include all patient consent forms.
• Please review the appendices before the meeting.
• Medical textbooks often have several appendices with reference tables.

Plural (Appendixes)

• I attached two appendixes to the email.
• The manual has three appendixes with troubleshooting tips.
• We only need a few appendixes for the final draft.

Common Mistakes

Many learners make errors with appendix because of its unusual plural forms. Here are the most frequent mistakes and how to fix them.

Mistake 1: Using “Appendices” as a Singular

Incorrect: The appendices is located at the end of the book.
Correct: The appendix is located at the end of the book. (singular)
Correct: The appendices are located at the end of the book. (plural)

Mistake 2: Using “Appendix” as a Plural

Incorrect: There are three appendix in the document.
Correct: There are three appendices in the document.
Correct: There are three appendixes in the document.

Mistake 3: Mixing Plural Forms in the Same Document

Inconsistent: The appendices are on page 10, and the appendixes are on page 20.
Consistent: The appendices are on page 10 and page 20.
Consistent: The appendixes are on page 10 and page 20.

Choose one plural form and stick with it throughout your writing.

Better Alternatives and When to Use Them

Sometimes you may want to avoid the appendix/appendices choice altogether. Here are simpler alternatives for different contexts.

For Documents

• Supplement – Use when the material is additional but not essential. Example: Please see the supplement for full details.
• Addendum – Use for a single addition to a contract or report. Example: The addendum clarifies the payment terms.
• Attachment – Use in emails or informal documents. Example: I have included the budget as an attachment.
• Supporting documents – Use for a group of materials. Example: The supporting documents are in the folder.

For Medical Contexts

• Vermiform appendix – The full medical name, but rarely needed in everyday conversation.
• Appendix organ – Use only if you need to distinguish from a document appendix. Example: The appendix organ was removed.

Formal vs. Informal Tone

The choice between appendices and appendixes often depends on how formal you want to sound.

Formal Tone (Use “Appendices”)

In academic papers, medical journals, legal documents, and official reports, appendices is the expected form. It sounds precise and professional.

Example: The appendices to this thesis include the survey instrument and raw responses.

Informal Tone (Use “Appendixes”)

In emails, casual conversation, blog posts, or internal memos, appendixes feels more natural. It avoids sounding overly academic.

Example: I added a couple of appendixes to the file so you can see the numbers.

Email Context

In email, you often refer to a single appendix or multiple attachments. If you use the word appendix, keep it simple.

Example: Please find the appendix attached. (singular)
Example: The appendixes are included in the PDF. (plural, informal)

Mini Practice: Check Your Understanding

Test yourself with these four questions. Answers are below.

Question 1

Which sentence is correct?
A. The report has two appendices.
B. The report has two appendix.

Question 2

Fill in the blank: The doctor said my _______ is inflamed.
A. appendix
B. appendices

Question 3

Which plural form is more appropriate for a medical journal article?
A. appendixes
B. appendices

Question 4

Is this sentence correct? “I need to review the appendices before the meeting.”
A. Yes
B. No

Answers

Answer 1: A. “Two appendices” is correct because appendix is singular and needs a plural form.

Answer 2: A. “My appendix” is singular, referring to one organ.

Answer 3: B. Appendices is the standard form in medical and academic writing.

Answer 4: A. Yes, the sentence is correct. Appendices is the plural form and works here.

Frequently Asked Questions

1. Is “appendix” ever plural?

No. Appendix is always singular. The plural forms are appendices or appendixes. You cannot use appendix to refer to more than one.

2. Which plural is more common in medical writing?

Appendices is far more common in medical writing. You will see it in textbooks, research papers, and clinical guidelines. Appendixes is rare in medical contexts.

3. Can I use “appendix” for both the body part and a document section?

Yes. The same word works for both meanings. Context makes the meaning clear. For example: My appendix was removed. (body part) vs. See the appendix for details. (document section).

4. What if I am writing for a general audience?

Use appendixes for a general audience. It sounds less formal and is easier to understand. If you are writing for doctors, researchers, or lawyers, use appendices.

Final Tip

When in doubt, remember this simple rule: Appendix is singular. For plural, choose appendices for formal writing and appendixes for everything else. Stick with one form in each document, and you will sound natural and correct.

For more help with singular and plural forms, visit our Singular or Plural Checks section. You can also explore Plural Spelling Rules for other tricky words. If you have questions, check our FAQ page or contact us.