Appendices and appendix can be confusing when you are writing a research paper, report, book, or other formal document. The key difference is that appendix is singular, while appendices and appendixes are both accepted plural forms. Although the two plurals are grammatically correct, they are not equally common in every context.

If you are preparing an academic assignment, appendices and appendix are the forms you will most often need to understand. This guide explains the difference, shows you how to use each word correctly, and provides practical examples to help you avoid common grammar mistakes.

1. Appendix vs. Appendices: What Is the Difference?

The main difference is the number of items being discussed. Appendix refers to one item, while appendices refers to more than one. The alternative plural, appendixes, is also correct.

An appendix usually contains supplementary information placed at the end of a book, report, dissertation, or research paper. The word can also refer to the small organ attached to the large intestine.

For academic and professional documents, appendices is a familiar choice. When discussing the anatomical organ, appendixes is also commonly used.

2. Is Appendix Singular or Plural?

Appendix is singular. Use it when referring to one supplementary section or one anatomical organ.

For example:

• The appendix contains additional research findings.
• The student added an appendix to the assignment.
• The doctor examined the patient’s appendix.

When you refer to multiple items, choose appendices or appendixes.

• The appendices contain the supporting documents.
• The textbook explains disorders affecting the appendix.
• The handbook includes several appendixes.

Remember that the surrounding sentence determines whether the noun should be singular or plural. Using the correct form makes your writing clearer and helps you avoid subject-verb agreement errors.

3. Why Are Both Appendices and Appendixes Correct?

English has several ways to form plural nouns. Most nouns become plural by adding -s or -es, which explains the form appendixes.

However, some English words retain plural patterns associated with their Latin origins. Appendices follows this traditional pattern.

Both forms are established in English, so neither is automatically a grammatical mistake. Their frequency depends partly on context, audience, and editorial preference.

The important distinction is between a grammatical rule and a style preference. A university may prefer appendices in academic work, but that does not make appendixes universally incorrect.

4. When Should You Use Appendices?

Use appendices when you need a conventional plural for supplementary material in formal writing. It is particularly familiar in research papers, dissertations, books, reports, and academic assignments.

For example:

• The research paper includes two appendices.
• Please read the appendices before reviewing the conclusion.
• The appendices contain the complete questionnaire and data tables.
• Three appendices provide further evidence for the study’s findings.

Each appendix may contain supporting information that would interrupt the main discussion if included in the body of the document.

If you are unsure which form to choose for a school assignment, research paper, or professional report, appendices is generally a reliable option. Always follow your institution’s formatting requirements if they specify a preference.

5. When Is Appendixes the Better Choice?

Appendixes is a natural plural when discussing multiple anatomical appendixes. It is also an accepted alternative when referring to supplementary sections in written documents.

Consider these examples:

Medical context

• The textbook discusses conditions affecting the appendix.
• The researchers examined the appendixes of the specimens.

Books and documents

• The handbook contains several appendixes.
• The publisher included appendixes with additional technical information.

Notice that appendixes is not restricted to medical writing. It can be used in reports and books, too. However, if a publisher, teacher, or organization requires appendices, use that form throughout the relevant document.

6. Common Grammar Mistakes to Avoid

Understanding the plural forms is only part of using appendix correctly. You must also pay attention to sentence structure, verb agreement, and consistency.

Mistake 1: Treating appendix as plural

Incorrect: The appendix contain the survey results.

Correct: The appendix contains the survey results.

Because appendix is singular, it takes the singular verb contains.

Mistake 2: Using a singular verb with appendices

Incorrect: The appendices contains additional information.

Correct: The appendices contain additional information.

Both appendices and appendixes take plural verbs when they function as plural subjects.

Mistake 3: Assuming appendixes is always wrong

Incorrect assumption: Only appendices is grammatically acceptable.

Correction: Both forms are accepted. Choose the form that fits the context and any applicable style requirements.

Mistake 4: Switching between plural forms unnecessarily

Inconsistent: The report contains three appendices. The appendixes are listed after the references.

Better: The report contains three appendices. The appendices are listed after the references.

Using one form consistently for the same material makes a document easier to read and edit.

For more practical explanations of commonly confused English words, explore [Latest Article].

7. How to Use Appendix and Its Plurals in Academic Writing

When writing an assignment, thesis, dissertation, or research report, choose your terminology before finalizing the document. This is especially important if your work contains multiple supplementary sections.

Here are a few practical guidelines:

• One section: Write Appendix A or an appendix.
• Multiple sections: Write Appendices A–C or the appendices.
• Numbered or lettered labels: Follow the required style guide or the institution’s formatting instructions.
• Supporting evidence: Place supplementary tables, questionnaires, transcripts, or other relevant material in an appendix when appropriate.
• Consistency: Use the same plural form throughout your document unless a specific distinction justifies a change.

For example, you might write, “Appendix A contains the survey questions, while Appendix B presents the additional data tables.”

When referring to both sections together, you could write, “The appendices provide supplementary information for the study.”

Keep in mind that an appendix should support the main discussion rather than replace essential explanations that belong in the body of the paper.

Frequently Asked Questions

Is appendix singular or plural?

Appendix is singular. It refers to one supplementary section or one anatomical organ. Its accepted plural forms are appendices and appendixes.

Which is correct: appendices or appendixes?

Both are correct. Appendices is widely used for supplementary sections in academic and professional documents, while appendixes is especially familiar in anatomical contexts. Either form can refer to document sections.

Should I use appendices or appendix in a research paper?

Use appendix when referring to one supplementary section and appendices when referring to multiple sections. Follow your institution’s or publisher’s formatting requirements.

Is appendixes grammatically incorrect?

No. Appendixes is an accepted plural of appendix. It is not automatically incorrect in formal writing, although appendices may be the preferred form in academic documents.

What is the plural of appendix in British English?

Both appendices and appendixes are recognized plural forms in British English. The preferred choice may depend on the context and the publication’s editorial conventions.

Do appendices and appendixes mean different things?

They generally have the same basic meaning when referring to supplementary document sections. Their main difference is conventional usage rather than a strict difference in definition.

Can I use appendices and appendixes in the same document?

You generally should choose one form and use it consistently when referring to the same type of material. Follow your required style guide if it specifies a particular form.

Conclusion

Appendix is singular, while appendices and appendixes are both correct plurals. For research papers, dissertations, reports, and books, appendices is usually the familiar choice. For anatomical discussions, appendixes is also a natural option.

The simplest approach is to consider your context, follow any required style guide, and remain consistent throughout your writing.