What Is the Plural of Appendix?
The word appendix has two standard plural forms: appendices and appendixes. Both are correct, but they are used in different contexts. Appendices is the traditional Latin plural and is preferred in academic and formal writing, especially when referring to supplementary material at the end of a book or document. Appendixes is the English plural form and is more common in general, informal, or medical contexts, such as when talking about the human appendix.
Quick Answer
Use appendices for formal academic writing, research papers, and books. Use appendixes for everyday conversation, medical references, and informal writing. Both are acceptable, but choosing the right one depends on your audience and tone.
Understanding the Two Plurals
The reason for two plural forms comes from the word’s origin. Appendix is a Latin word that entered English. In Latin, nouns ending in -ix often change to -ices in the plural. This gives us appendices. Over time, English speakers also applied the regular English plural rule (adding -es), creating appendixes.
Today, both forms are widely accepted, but they carry different stylistic weights. Knowing when to use each will make your writing sound more natural and appropriate.
When to Use Appendices
Appendices is the go-to choice for formal, academic, and professional writing. You will see it in textbooks, research papers, legal documents, and official reports. It signals that the writer is following traditional academic conventions.
- Formal tone: “Please refer to the appendices at the end of the report.”
- Academic context: “The appendices contain the raw data and survey questions.”
- Book publishing: “The appendices include maps and historical timelines.”
When to Use Appendixes
Appendixes is the standard plural in medical and everyday English. If you are talking about the human body, use appendixes. It also works well in informal emails, blog posts, and casual conversation.
- Medical context: “The surgeon removed both appendixes during the operation.”
- Informal email: “I attached the appendixes to the email.”
- Conversation: “How many appendixes does a person have?”
Comparison Table: Appendices vs. Appendixes
| Feature | Appendices | Appendixes |
|---|---|---|
| Origin | Latin plural | English plural |
| Formality | Formal, academic | Informal, general |
| Common use | Books, research papers, legal docs | Medical, conversation, emails |
| Example sentence | The appendices provide supporting evidence. | He had both appendixes removed. |
| Frequency in writing | More common in published academic work | More common in everyday speech |
Natural Examples
Seeing the words in real sentences helps you understand the nuance. Below are examples for both forms in different contexts.
Examples with Appendices
- “The thesis includes three appendices with interview transcripts.”
- “All appendices must be numbered and listed in the table of contents.”
- “The appendices to the contract clarify the payment terms.”
- “Students should review the appendices before the exam.”
Examples with Appendixes
- “The doctor said both appendixes were inflamed.”
- “I checked the appendixes in the user manual, but they were not helpful.”
- “How many appendixes does the human body have? Usually one, but some people have two.”
- “The appendixes in that guide are outdated.”
Common Mistakes
Even advanced English learners sometimes make errors with these plurals. Here are the most frequent mistakes and how to avoid them.
Mistake 1: Using Appendices for the Human Body
Incorrect: “The patient had two appendices removed.”
Correct: “The patient had two appendixes removed.”
Why: Medical professionals almost always use appendixes for the body part. Using appendices in a medical context sounds odd and overly academic.
Mistake 2: Using Appendixes in Formal Academic Papers
Incorrect: “The appendixes are located after the bibliography.”
Correct: “The appendices are located after the bibliography.”
Why: Most style guides (APA, MLA, Chicago) recommend appendices for academic writing. Using appendixes may look less polished.
Mistake 3: Confusing Appendix with Appendage
Incorrect: “The book has several appendages.”
Correct: “The book has several appendices.”
Why: Appendage refers to a body part like an arm or leg, not supplementary material. Keep these words separate.
Mistake 4: Forgetting the Singular Form
Incorrect: “One of the appendices is missing.” (This is actually correct, but some learners think appendices is only plural.)
Correct: “One appendix is missing.” (Singular) / “Two appendices are missing.” (Plural)
Why: Appendices is the plural of appendix. The singular form is always appendix.
Better Alternatives and When to Use Them
Sometimes you may want to avoid the confusion altogether. Here are some alternatives that work in specific contexts.
For Academic Writing
- Supplementary materials – A clear, modern alternative. Example: “The supplementary materials include charts and graphs.”
- Addenda – Used for additions to a document, especially in legal or publishing contexts. Example: “The addenda to the report were approved.”
For Medical Contexts
- Vermiform appendix – The full medical term. Example: “The vermiform appendix was removed.”
- Appendices (body part) – Rarely used; stick with appendixes.
For General Writing
- Back matter – Refers to material at the end of a book. Example: “The back matter includes an index and glossary.”
- Attachments – Good for emails. Example: “Please see the attachments for details.”
Mini Practice: Test Your Knowledge
Choose the correct plural form for each sentence. Answers are below.
- The research paper has two (appendices / appendixes) with survey data.
- The doctor said both (appendices / appendixes) were healthy.
- Please check the (appendices / appendixes) at the end of the book.
- How many (appendices / appendixes) does a typical person have?
Answers
- Appendices – Academic context.
- Appendixes – Medical context.
- Appendices – Formal book reference.
- Appendixes – General question about the body.
Frequently Asked Questions
1. Is “appendices” the only correct plural?
No. Both appendices and appendixes are correct. The choice depends on context. Appendices is preferred in formal writing, while appendixes is common in medical and informal settings.
2. Can I use “appendix” as a plural?
No. Appendix is singular. The plural forms are appendices or appendixes. Using appendix for more than one is a grammatical error.
3. Which plural is used in APA style?
APA style recommends appendices. This is consistent with most academic style guides. Always check your specific style guide if you are writing a paper.
4. Do British and American English differ in their use?
Both forms are used in British and American English. However, appendices is slightly more common in British academic writing, while appendixes is more frequent in American medical writing. The difference is small and not a strict rule.
Final Tip
When in doubt, consider your audience. If you are writing a formal document, a research paper, or a book, choose appendices. If you are writing an email, a blog post, or talking about the human body, choose appendixes. Both are correct, but using the right one shows you understand the nuance.
For more help with tricky plural forms, explore our guides on Common Plural Forms or check our FAQ for quick answers. If you have a specific question, feel free to contact us.
