If you are unsure whether to write appendices or appendixes, the good news is that both forms are correct. They are the plural forms of appendix, a word commonly used for additional sections at the end of a report, book, thesis, or research paper. The main difference is their linguistic origin and usage, not their meaning.
Appendices is traditionally preferred in academic and formal writing, while appendixes follows the regular English plural pattern. However, neither form is grammatically wrong. Understanding how to use them, when to choose one over the other, and how to keep your writing consistent will help you avoid common grammar mistakes.
1. Appendices or Appendixes: Which Is Correct?
Both appendices and appendixes are accepted plural forms of appendix in modern English. You can use either word when referring to two or more supplementary sections in a document.
The choice usually depends on the context, the publication’s style guide, and your personal preference.
- Appendices: The traditional Latin-derived plural, commonly used in academic papers, dissertations, technical reports, and formal publications.
- Appendixes: The regular English plural, formed by adding -es to the singular noun, and also acceptable in general and professional writing.
For example:
- The research paper contains three appendices with supporting data.
- The instruction manual includes two appendixes explaining the equipment.
Both sentences are grammatically correct. The words communicate the same meaning, so you do not need to worry about choosing the wrong form simply because one looks more traditional.
2. What Does Appendix Mean?
An appendix is supplementary material placed at the end of a book, report, essay, or another document. It contains information that supports the main text but would make the central discussion unnecessarily long or difficult to follow if included in the main body.
An appendix might contain:
- Detailed tables or statistical results
- Survey questions and questionnaire responses
- Technical explanations
- Supporting documents
- Additional examples or calculations
- Research methods and supplementary information
For instance, a student writing a research paper might discuss the main findings in the body of the paper and place the full questionnaire in an appendix.
The word appendix can also refer to a small organ attached to the large intestine. In anatomy, the same plural alternatives exist, although the appropriate wording may depend on the medical context.
Remember that appendix refers to one item, while appendices and appendixes refer to multiple items.
3. The Grammar Rules Behind Appendices and Appendixes
The difference between these two forms comes from how English handles plural nouns borrowed from other languages.
How appendices is formed
Appendices follows a traditional Latin plural pattern. The singular word appendix becomes appendices, reflecting the classical plural form associated with Latin words ending in -ex or -ix.
This pattern also appears in other English words, including:
- Index → indices
- Matrix → matrices
- Vertex → vertices
These traditional forms are especially familiar in scholarly, mathematical, scientific, and technical writing, although the preferred plural can vary by word and context.
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How appendixes is formed
Appendixes follows a regular English plural pattern. For many nouns ending in x, English adds -es to make the plural.
Examples include:
- Box → boxes
- Fox → foxes
- Tax → taxes
- Appendix → appendixes
This makes appendixes straightforward to understand and form. It is not an incorrect alternative or a grammatical mistake.
The key lesson is that English sometimes preserves traditional plural forms while also accepting forms created through its regular grammatical rules.
4. Appendices vs. Appendixes: Key Differences
Although the two words have the same basic meaning, their usage can differ slightly in practice.
| Feature | Appendices | Appendixes |
|---|---|---|
| Singular form | Appendix | Appendix |
| Plural formation | Traditional Latin-derived form | Regular English form |
| Meaning | Multiple supplementary sections or organs | Multiple supplementary sections or organs |
| Academic writing | Commonly preferred | Also acceptable |
| General writing | Correct | Correct |
| Grammatical status | Correct | Correct |
The most important distinction is convention rather than correctness. Appendices often feels more familiar in scholarly writing, but appendixes remains a valid English plural.
If you are writing for a university, publisher, employer, or professional organization, check its style requirements before making your choice.
5. When Should You Use Appendices or Appendixes?
Choosing the right form is usually simple once you know your audience and the type of document you are preparing.
Use appendices in formal and academic writing
Appendices is a sensible default for documents such as:
- University essays and dissertations
- Scientific research papers
- Academic books
- Formal business reports
- Technical documentation
For example:
“The appendices contain the complete survey results and additional statistical tables.”
This wording fits a research document and follows a familiar academic convention.
Use appendixes when it suits your writing style
Appendixes is also appropriate when a writer or publication prefers regular English plurals.
For example:
“The equipment guide includes two appendixes with extra troubleshooting instructions.”
This sentence is correct and clear. There is no need to change appendixes simply to make the sentence sound more professional.
Follow your required style guide
When preparing an academic assignment or submitting a manuscript, follow the institution’s or publisher’s instructions. Some publications specify particular terminology and formatting conventions.
If no preference is given, choose one form and use it consistently throughout the document.
For more practical explanations of commonly confused English expressions, explore [Latest Article].
6. Common Mistakes to Avoid
Even though both plural forms are correct, writers can still make mistakes when using appendix in sentences or organizing supplementary material.
Mistake 1: Using appendix for multiple items
Incorrect: The report contains three appendix.
Correct: The report contains three appendices.
You could also write “three appendixes.” Both plural forms work.
Mistake 2: Writing appendixs
Incorrect: The book includes two appendixs.
Correct: The book includes two appendices or two appendixes.
The form appendixs is not a standard plural.
Mistake 3: Mixing plural forms without a reason
Using appendices in one section and appendixes in another may make a document look inconsistent. Choose a form and maintain it throughout unless a specific title, quotation, or editorial requirement calls for something different.
Mistake 4: Assuming appendixes is always informal
Although appendices is common in academic writing, appendixes is not inherently unprofessional. Both are accepted forms.
Mistake 5: Confusing an appendix with an attachment
An appendix is typically an organized section of a larger document. An attachment is a separate item included with a message, email, or other communication. The terms may overlap in some situations, but they are not always interchangeable.
7. Examples of Appendices and Appendixes in Sentences
The following examples show how both plural forms work in everyday and professional English.
Examples using appendices
- The dissertation includes three appendices containing additional research materials.
- Please consult the appendices for the complete survey questionnaire.
- The author placed the detailed calculations in the appendices.
- All appendices must follow the university’s formatting requirements.
- The report’s appendices provide further evidence for the main findings.
Examples using appendixes
- The manual contains two appendixes with installation instructions.
- The book’s appendixes explain several technical terms.
- We reviewed the appendixes before publishing the report.
- The document includes additional diagrams in its appendixes.
- The reference guide has several appendixes for readers who need more detail.
Notice that the meaning remains the same in both sets. The choice affects the plural form, not the information being communicated.
Frequently Asked Questions
Is appendices or appendixes more correct?
Both are correct. Appendices is a traditional Latin-derived plural and is common in academic writing. Appendixes follows regular English pluralization rules and is also accepted.
Is appendixes a real word?
Yes. Appendixes is a standard English plural of appendix. It is not a spelling error, even though some academic publications prefer appendices.
What is the singular form of appendices?
The singular form is appendix. For example, “The report contains one appendix” is correct, while “The report contains three appendices” uses the plural form.
Can I use appendices in a university essay?
Yes. Appendices is a common and suitable choice for essays, dissertations, theses, and research papers. Always follow your institution’s specific formatting guidelines.
Is appendixs ever correct?
No. Appendixs is not a standard plural form. Use appendices or appendixes instead.
Do appendices and appendixes have different meanings?
No. When referring to the plural of appendix, both words have the same meaning. The difference concerns their formation and usage conventions.
Should I use appendices or appendixes in a business report?
Either form can work. Appendices is a familiar choice for formal reports, while appendixes is also grammatically acceptable. Follow your organization’s style guide if one exists.
What is the plural of appendix in anatomy?
Both appendices and appendixes are recognized plural forms of appendix. In medical writing, follow the terminology and style conventions used by the relevant institution or publication.
Conclusion
Both appendices and appendixes are correct plural forms of appendix. The traditional form appendices is widely used in academic and formal writing, while appendixes follows the regular English plural pattern. Neither is inherently wrong or less professional in every context.
For a university paper, research project, or formal report, appendices is a practical default. If your publication prefers appendixes, you can use that form with confidence. Above all, follow the relevant style guide and remain consistent throughout your writing.
