Common Mistakes with the Plural of Appendix

The most common mistake with the plural of “appendix” is using “appendices” when you mean “appendixes,” or vice versa, without understanding the context. The correct plural depends entirely on whether you are writing about human anatomy (medical context) or supplementary material in a book or document (publishing context). In medicine, the standard plural is appendixes. In publishing, the standard plural is appendices. Using the wrong form can confuse your reader or make your writing sound unprofessional.

Quick Answer: Which Plural Should You Use?

Use appendixes when referring to the organ in the human body (e.g., “The surgeon removed two inflamed appendixes”). Use appendices when referring to supplementary sections at the end of a book, report, or document (e.g., “The appendices contain the raw data from the study”). If you are unsure, remember that medical writing almost always prefers “appendixes,” while academic and business writing almost always prefers “appendices.”

Understanding the Two Plurals

The word “appendix” comes from Latin, and like many Latin-derived words, it has two accepted plural forms: the English-style plural (appendixes) and the Latin-style plural (appendices). Both are grammatically correct, but they are not interchangeable. The choice is driven by the field of use.

Appendixes (Medical Context)

In medicine, “appendix” refers to the small, finger-shaped pouch attached to the large intestine. When a doctor or medical writer needs to refer to more than one of these organs, the standard plural is appendixes. This is the form used in medical journals, surgical reports, patient records, and anatomy textbooks.

Formal/Informal Tone: “Appendixes” is the standard formal term in medical writing. It is also used in informal medical conversation among healthcare professionals.

Email/Conversation Context: In an email to a colleague, you might write, “We saw two patients with inflamed appendixes this morning.” In a conversation, you would say, “The CT scan showed two appendixes.”

Appendices (Publishing Context)

In publishing, academic writing, and business documentation, “appendix” refers to a section of supplementary material at the end of a book or document. The standard plural for this meaning is appendices. This is the form used in textbooks, research papers, corporate reports, and style guides.

Formal/Informal Tone: “Appendices” is the formal standard in academic and professional writing. In very informal notes, some writers might use “appendixes,” but this is less common and can look careless.

Email/Conversation Context: In a formal email, you might write, “Please refer to the appendices for the full questionnaire.” In a conversation, you might say, “The appendices are at the back of the report.”

Comparison Table: Appendixes vs. Appendices

Natural Examples

Here are examples showing how each plural is used in real writing and speech.

Examples of “Appendixes” (Medical)

• “During the autopsy, the pathologist noted that both appendixes showed signs of chronic inflammation.”
• “The surgical team removed three appendixes from different patients in one day.”
• “In rare cases, a person can be born with two appendixes.”
• “The radiology report mentioned that the appendixes were normal in size and appearance.”

Examples of “Appendices” (Publishing)

• “The appendices at the end of the textbook contain the periodic table and a glossary of terms.”
• “Please check the appendices for the full interview transcripts.”
• “The report has five appendices, including financial statements and legal disclaimers.”
• “The author added two new appendices to the second edition of the book.”

Common Mistakes

Here are the most frequent errors learners make with the plural of “appendix.”

Mistake 1: Using “Appendices” in Medical Writing

Incorrect: “The surgeon removed the patient’s appendices.”
Correct: “The surgeon removed the patient’s appendixes.”
Why: In a medical context, “appendices” sounds like you are talking about document sections, not organs. It can confuse other healthcare professionals.

Mistake 2: Using “Appendixes” in Academic Writing

Incorrect: “The appendixes of the thesis contain the raw data.”
Correct: “The appendices of the thesis contain the raw data.”
Why: In academic and publishing contexts, “appendices” is the expected form. Using “appendixes” here can make your writing look informal or unedited.

Mistake 3: Mixing Both Forms in the Same Document

Incorrect: “The report has three appendixes, and the medical records show two appendices.”
Correct: “The report has three appendices, and the medical records show two appendixes.”
Why: Consistency matters. Use “appendices” for documents and “appendixes” for organs, but do not swap them within the same context.

Mistake 4: Using “Appendix” as a Plural

Incorrect: “There are two appendix in the book.”
Correct: “There are two appendices in the book.”
Why: “Appendix” is singular. You must add the correct plural ending.

Better Alternatives and When to Use Them

In some situations, you can avoid the confusion entirely by rephrasing. Here are some alternatives.

For Medical Context

• Use “vermiform appendixes” – This is the full anatomical term and leaves no doubt you are talking about the organ. Example: “The patient had two vermiform appendixes.”
• Use “appendix organs” – A clear, simple alternative. Example: “Both appendix organs were removed.”

For Publishing Context

• Use “supplementary materials” – A general term that avoids the plural issue. Example: “The supplementary materials are available online.”
• Use “additional sections” – Clear and straightforward. Example: “The additional sections include the data tables.”

When to use these alternatives: Use them when you are writing for a general audience that may not know the difference between “appendixes” and “appendices.” In formal medical or academic writing, stick with the standard plurals.

Mini Practice: Test Your Understanding

Choose the correct plural for each sentence. Answers are below.

1. The surgeon removed two inflamed _______. (appendixes / appendices)
2. Please refer to the _______ at the end of the report. (appendixes / appendices)
3. In rare cases, a person can have three _______. (appendixes / appendices)
4. The book’s _______ contain the author’s notes. (appendixes / appendices)

Answers

1. appendixes – Medical context (organs).
2. appendices – Publishing context (document sections).
3. appendixes – Medical context (organs).
4. appendices – Publishing context (document sections).

Frequently Asked Questions (FAQ)

1. Is “appendices” ever correct in medical writing?

No, not when referring to the organ. In medical writing, “appendices” is almost never used for the anatomical appendix. If you see “appendices” in a medical text, it is almost certainly referring to supplementary document sections, such as in a research paper’s appendices.

2. Can I use “appendixes” for a book’s supplementary sections?

Technically yes, but it is not recommended. Some dictionaries accept “appendixes” as a plural for both meanings, but in practice, using “appendixes” for document sections can look informal or careless. For academic and professional writing, always use “appendices.”

3. What is the plural of “appendix” in British English?

The same rule applies in British English. “Appendixes” is used for the organ, and “appendices” is used for document sections. British style guides, such as the Oxford Style Manual, recommend “appendices” for publishing contexts.

4. How do I remember which plural to use?

Think of the letter “i” in “appendices” as standing for “information” (documents contain information). Think of the letter “e” in “appendixes” as standing for “excision” (surgical removal of the organ). This simple memory trick can help you choose the correct form quickly.

For more guidance on confusing plurals, visit our Confusing Plurals section. If you have questions about other plural forms, check our Common Plural Forms page. For general questions about our content, see our FAQ page.