If you are writing a report, research paper, book, or other document, you may wonder whether the plural of appendix should be appendices or appendixes.
The good news is that both forms are correct in standard English. The choice is mainly influenced by meaning, context, and editorial style.
For supplementary sections at the end of a document, appendices is a familiar and widely used choice, especially in academic and formal writing. Appendixes is also a valid plural and appears in standard English, including professional and editorial writing.
Quick Answer
Both appendices and appendixes are correct plural forms of appendix.
For a book, report, thesis, or research paper, appendices is a particularly common choice:
The report contains three appendices.
Appendixes is also grammatically correct:
The report contains three appendixes.
For the anatomical meaning, appendixes is commonly used, although appendices is also recognized.
So, do not treat appendixes as a spelling mistake. If a particular publication, school, employer, or style guide specifies one form, follow that preference and use it consistently.
Why People Confuse Them
The confusion comes from the fact that appendix has two established plural forms.
Appendices follows the traditional plural pattern associated with the word’s Latin history. Appendixes uses a regular English plural ending.
That gives English two accepted forms rather than one mandatory plural.
There is also a meaning-based pattern that makes the choice less obvious. Dictionaries commonly associate appendices with supplementary sections in books and documents, while appendixes is often used for the anatomical sense.
However, this is a usage tendency, not a universal rule.
Key Differences At A Glance
| Feature | Appendices | Appendixes |
|---|---|---|
| Grammatical status | Correct plural | Correct plural |
| Document sections | Very common | Also correct |
| Academic writing | Common choice | Acceptable depending on style |
| Anatomy | Possible | Common choice |
| Pronunciation | /əˈpɛn.də.siːz/ | /əˈpɛn.dɪk.səz/ |
The most important point is that neither form is automatically wrong.
Meaning and Usage Difference
Appendices and appendixes are both plural forms of appendix. They do not represent two completely different meanings.
When appendix means a supplementary section at the end of a document, appendices is a very familiar choice:
The study includes two appendices with additional tables.
But appendixes can also be used for the same meaning:
The manual contains several appendixes with detailed instructions.
When appendix refers to the body organ, appendixes is commonly used:
The surgeon examined the patient’s inflamed appendixes.
The form appendices is also recorded for the anatomical sense, so it would be too strong to call it incorrect.
Compact comparison
- Appendices: especially familiar for multiple supplementary sections in books, reports, and academic documents.
- Appendixes: a fully established plural that is also used for documents and is especially common for the anatomical meaning.
Tone, Context, and Formality
Appendices can sound more traditional or formal, particularly when discussing research papers, scholarly books, reports, or other structured documents.
For example:
See Appendices A and B for the complete survey results.
Appendixes does not make a sentence grammatically informal or incorrect. It is a standard plural and may be required or preferred by a particular publication’s house style.
For example, the Chicago Manual of Style and MLA materials use appendixes in their editorial discussions.
The safest approach is to consider your document’s established style. If the document already uses appendices, continue with that form. If its style specifies appendixes, use that form instead.
Which One Should You Use?
For most US writers referring to several supplementary sections in a report, thesis, book, or research paper, appendices is a natural choice.
Use:
The appendices contain the full survey data.
You can also correctly write:
The appendixes contain the full survey data.
For anatomy, appendixes is a particularly familiar choice:
The patient had both appendixes removed.
The important distinction is not “correct versus incorrect.” Instead, consider context and style preference.
If your instructor, publisher, employer, or organization has a stated preference, that preference should guide your choice.
When One Choice Sounds Wrong
There are situations where one form may sound less natural because of the context.
For example, appendices may feel more expected in an academic sentence such as:
The appendices provide detailed statistical information.
That does not make appendixes grammatically wrong. It simply may not match the preferred style of a particular academic or professional publication.
Likewise, appendixes may sound more natural in an anatomical sentence:
The patient had two abnormal appendixes.
Again, this is a usage preference rather than a universal grammar prohibition.
The key mistake is assuming that one plural must always replace the other.
Common Mistakes (and Quick Fixes)
Mistake: Calling appendixes incorrect.
Fix: Both appendices and appendixes are established plural forms.
Mistake: Using the singular after a plural number.
Wrong: The report contains three appendix.
Correct: The report contains three appendices.
Also correct: The report contains three appendixes.
Mistake: Switching forms without a reason.
A document that repeatedly changes between appendices and appendixes can look inconsistent.
Fix: Pick the form that fits your style and use it consistently.
Mistake: Assuming anatomy requires one form everywhere.
Although appendixes is commonly associated with the anatomical meaning, dictionaries recognize both forms.
Everyday Examples
Here are natural examples from different contexts:
- The research paper includes two appendices with supporting data.
- Please review Appendices A and B before the meeting.
- The publisher added several appendixes to the technical manual.
- The surgeon examined the patient’s inflamed appendixes.
- The report’s appendices contain the original questionnaires.
- The online reference has several appendixes covering additional material.
- The professor asked students to label their appendices clearly.
- The medical report described abnormalities affecting both appendixes.
These examples show why context and editorial preference matter more than a simple “right or wrong” rule.
Dictionary-Style Word Details
Verb
Appendices: Not commonly used as a verb in standard US English.
Appendixes: Not commonly used as a verb in standard US English.
Both are plural noun forms. They are not verb forms.
Noun
Appendices: The plural of appendix, commonly used for multiple supplementary sections in books, reports, papers, and other documents.
Appendixes: Another accepted plural of appendix, used for supplementary sections and also commonly used for the anatomical sense.
Synonyms
For the document sense, closest plain alternatives include supplement, addition, addendum, and supplementary section, depending on the exact context.
These are not perfect substitutes in every sentence.
For the anatomical sense, there is no ordinary synonym that can replace appendixes naturally in most everyday sentences.
Example Sentences
Appendices: The final chapter refers readers to the appendices for the complete data.
Appendixes: The medical team documented abnormalities in both appendixes.
Appendices: The book’s appendices contain several detailed charts.
Appendixes: The technical guide includes several appendixes for reference.
Word History
Appendix entered English from Latin. Its traditional plural appendices reflects the Latin plural pattern, while appendixes developed as a regular English plural.
The modern language therefore recognizes both forms. Their usage can vary according to meaning, field, and editorial preference.
Phrases Containing
Common expressions include:
- appendix A
- appendix B
- Appendices A and B
- the appendices of a report
- the appendixes of a manual
- multiple appendixes
- an appendix to a book
- refer to the appendices
When referring to one section, use the singular appendix. When referring to multiple sections, use either accepted plural according to the chosen style.
FAQs
Are appendices and appendixes both correct?
Yes, both appendices and appendixes are correct plural forms of appendix. Neither should automatically be marked as a spelling or grammar error. The choice depends on context, established usage, and the editorial style you are following.
Which form should I use in an academic paper?
Appendices is a very common choice for academic papers, research reports, and similar documents. However, appendixes is also an accepted plural. If your instructor, journal, or institution has a stated preference, follow that preference consistently.
Is appendixes preferred for the body part?
Appendixes is commonly used for the anatomical meaning of appendix. This is a useful tendency to remember, but it is not an absolute rule. Major dictionaries also recognize appendices for the anatomical sense, so the alternative is not automatically incorrect.
Can appendices and appendixes be used interchangeably?
They can often be used interchangeably when referring to multiple supplementary sections. However, individual publications may prefer one form. Switching between forms within the same document can create unnecessary inconsistency, so choose one according to your context.
How do you pronounce appendices and appendixes?
Appendices is pronounced roughly “uh-PEN-duh-seez,” while appendixes is pronounced roughly “uh-PEN-dik-siz.” The difference is noticeable in the final portion of the word, so they should not be treated as alternate pronunciations of the same spelling.
Should I use the same form throughout one document?
Yes. Consistency is the practical choice when both forms are acceptable. If you begin a report with appendices, continue using appendices when referring to multiple sections. Do the same with appendixes if that is your selected form.
Conclusion
Appendices and appendixes are both correct plural forms of appendix in US English.
For supplementary sections in academic and formal documents, appendices is a familiar and widely used choice. Appendixes is also standard and may be preferred by particular publications or styles.
For the anatomical meaning, appendixes is especially common.
The simplest approach is to choose the form that fits your context and follow your publication or organization’s style consistently.
