Appendices vs Appendixes: Grammar Rules Made Simple

Have you ever wondered whether the correct plural of appendix is appendices or appendixes? If so, you’re not alone. This is one of the most common grammar questions among students, researchers, teachers, editors, and English learners.

Since both forms appear in dictionaries, books, and academic publications, many people are unsure which one is appropriate in formal writing.

The confusion exists because appendix is a word borrowed from Latin. Like many Latin-origin words in English, it has retained its traditional Latin plural while also developing a modern English plural. As a result, both “appendices” and “appendixes” are grammatically correct, but they are not always used in the same situations.

If you’re writing a thesis, dissertation, research paper, business report, university assignment, or professional document, choosing the correct plural form can make your writing more accurate and professional.

In this complete grammar guide, you’ll learn:

• The correct plural of appendix
• The difference between appendices and appendixes
• Which form is preferred in academic writing
• British vs American English usage
• Grammar rules
• Latin origin
• Pronunciation
• Practical examples
• Common mistakes
• Easy memory tricks
• Frequently asked questions

By the end of this guide, you’ll know exactly which form to use in every situation.

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Appendices or Appendixes – Quick Answer

Both appendices and appendixes are correct plural forms of the noun appendix. The best choice depends on where and how you’re using the word.

At a Glance

Question	Answer
Is appendices correct?	✅ Yes
Is appendixes correct?	✅ Yes
Which is more formal?	Appendices
Which is preferred in academic writing?	Appendices
Which is common in everyday English?	Appendixes
Which should students use?	Appendices
Meaning of appendix	Extra information added to the end of a document

Simple Rule

• Appendices is the preferred choice for academic, scientific, legal, and professional writing.
• Appendixes is commonly used in general English and informal American writing.

Examples

✅ The dissertation contains three appendices with survey results.

✅ The instruction manual includes two appendixes for additional information.

Both sentences are grammatically correct. However, the first sounds more formal and is preferred in academic writing.

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What Does “Appendix” Mean?

The word appendix has two different meanings in English.

1. Appendix in Writing

In writing, an appendix is an additional section placed at the end of a book, report, thesis, dissertation, or research paper. It contains supporting information that helps readers understand the main content without interrupting its flow.

An appendix may include:

• Tables
• Charts
• Graphs
• Survey questionnaires
• Interview transcripts
• Images
• Maps
• References
• Statistical data

Example:

The research paper includes several appendices containing raw survey data.

2. Appendix in Human Anatomy

An appendix is also a small tube-shaped organ attached to the large intestine.

The plural of the medical term can also be:

• Appendices
• Appendixes

Medical textbooks often use appendices, while some healthcare professionals use appendixes in everyday communication.

Example:

The medical report discussed several inflamed appendixes observed during the study.

Both forms are accepted because they follow different pluralization rules.

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Why Do People Confuse Appendices and Appendixes?

Many English learners assume that only one form can be correct. In reality, the confusion exists because English combines both Latin and modern English grammar rules.

Here are the main reasons people get confused:

• The word comes from Latin.
• English accepts both Latin and English plural forms.
• Academic institutions usually prefer appendices.
• Some American publications use appendixes.
• Different dictionaries show different usage examples.
• Writers often see both forms in books and online articles.

Since both forms are grammatically correct, choosing the right one depends on the context rather than correctness.

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The Origin of Appendices and Appendixes

The word appendix comes from the Latin verb appendere, which means “to attach,” “hang upon,” or “add to.”

Originally, the word described something attached to another object. Over time, English adopted it to refer to additional material attached to books, reports, legal documents, and research papers.

As English evolved, two plural forms became accepted.

Latin Plural

Appendix → Appendices

Modern English Plural

Appendix → Appendixes

Both forms now appear in major dictionaries, although appendices remains the preferred option in formal writing.

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Grammar Rule Behind Appendices and Appendixes

Understanding the grammar rule makes this topic much easier.

Many nouns borrowed from Latin that end in -ix change their ending to -ices when made plural.

Examples include:

Singular	Latin Plural
Appendix	Appendices
Matrix	Matrices
Index	Indices
Vertex	Vertices
Cicatrix	Cicatrices

Modern English also accepts regular English plurals for several of these words.

Singular	Modern English Plural
Appendix	Appendixes
Matrix	Matrixes
Index	Indexes

This is why both appendices and appendixes are considered grammatically correct.

The Latin form is generally preferred in formal, academic, and scientific writing, while the English form is more common in everyday usage.

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Appendices vs Appendixes – What’s the Difference?

Although both words have the same meaning, they differ slightly in style and usage.

Feature	Appendices	Appendixes
Grammar	Latin plural	English plural
Formality	High	Medium
Academic writing	Preferred	Less common
Research papers	Preferred	Rare
Professional documents	Preferred	Acceptable
Everyday English	Common	Very common

Which One Should You Use?

Choose appendices if you’re writing:

• A thesis
• A dissertation
• A research paper
• A scientific journal article
• A university assignment
• A legal document

Choose appendixes if you’re writing:

• A blog post
• An email
• Informal content
• General business communication
• Everyday English

If you’re unsure which form to use, appendices is the safest and most professional choice.

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British English vs American English

Unlike words such as colour/color or centre/center, there is no strict British or American spelling difference between appendices and appendixes.

Instead, the preference depends on the writing style.

British English

British universities, publishers, and academic institutions usually prefer appendices, especially in scholarly writing.

American English

American English recognizes both forms.

However:

• Universities generally prefer appendices.
• Academic journals almost always use appendices.
• Informal writing may use appendixes more frequently.

Comparison Table

Context	Preferred Form
UK Universities	Appendices
Scientific Journals	Appendices
Research Papers	Appendices
Formal Reports	Appendices
Informal American Writing	Appendixes

If your audience is academic or professional, appendices is usually the better choice.

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Pronunciation of Appendices and Appendixes

Although both words have the same meaning, they are pronounced slightly differently.

Appendices

IPA: /əˈpen.dɪ.siːz/

Pronunciation: uh-PEN-di-seez

Appendixes

IPA: /əˈpen.dɪk.sɪz/

Pronunciation: uh-PEN-dik-siz

The pronunciation changes because each plural follows a different grammatical pattern. Despite this small difference, native English speakers understand both forms without confusion.

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When Should You Use Appendices?

Although both appendices and appendixes are grammatically correct, choosing the right one depends on your audience and the type of document you’re writing.

Use Appendices When:

The Latin plural appendices is the preferred choice in formal and academic writing. It is widely used by universities, publishers, researchers, and professional organizations because it follows the traditional grammatical form.

Use appendices in:

• Research papers
• Theses and dissertations
• Scientific journals
• Academic textbooks
• University assignments
• Technical reports
• Government publications
• Legal documents
• Professional manuals

Examples:

• The thesis includes four appendices containing survey responses.
• Please refer to the appendices for additional statistical analysis.
• Supporting documents are provided in the appendices.

Using appendices in these contexts makes your writing sound more formal, professional, and academically appropriate.

Use Appendixes When:

The English plural appendixes is acceptable in less formal writing and is more common in general American English.

Use appendixes in:

• Blog posts
• Informal reports
• Business emails
• Instruction manuals
• General articles
• Everyday communication

Examples:

• The user guide contains two appendixes with troubleshooting tips.
• Check the appendixes for additional product specifications.

Although appendixes is correct, many professional writers still prefer appendices because it is recognized internationally.

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When Should You NOT Use These Words?

Knowing when not to use these plurals is just as important.

Avoid using appendices or appendixes in these situations:

When Referring to Only One Appendix

Incorrect:

❌ The appendices is attached.

Correct:

✅ The appendix is attached.

When Mixing Both Forms in One Document

Incorrect:

❌ Chapter Five contains two appendices, while the report ends with three appendixes.

Correct:

✅ Chapter Five contains two appendices.

OR

✅ Chapter Five contains two appendixes.

Choose one style and use it consistently throughout your document.

When the Word Is Not Plural

Incorrect:

❌ Please read the appendices on page 85.

(when there is only one)

Correct:

✅ Please read the appendix on page 85.

Consistency is an important part of professional writing.

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Common Mistakes with Appendices and Appendixes

Even experienced writers sometimes make mistakes with these plural forms.

Here are some of the most common errors.

Mistake 1: Thinking One Form Is Wrong

Many people believe appendixes is incorrect.

This is false.

Both appendices and appendixes are accepted by major English dictionaries.

Mistake 2: Using “Appendixs”

Incorrect:

❌ appendixs

Correct:

✅ appendices

✅ appendixes

Mistake 3: Mixing Styles

Incorrect:

❌ See Appendix A and the appendixes in Chapter 6.

Correct:

✅ See Appendix A and the appendices in Chapter 6.

Mistake 4: Using the Singular for Multiple Sections

Incorrect:

❌ The report contains three appendix.

Correct:

✅ The report contains three appendices.

Mistake 5: Choosing the Less Formal Form in Academic Writing

Although acceptable, appendixes is usually not the preferred choice in university assignments or scholarly publications.

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Real-Life Examples of Appendices and Appendixes

The easiest way to remember grammar is by seeing words used naturally.

Academic Writing

• The dissertation contains five appendices.
• Refer to the appendices for complete survey results.
• Additional charts appear in the appendices.
• The professor reviewed every appendix before approving the appendices section.
• Statistical calculations are included in the appendices.

Research Papers

• Raw data is provided in the appendices.
• The interview transcripts appear in the appendices.
• Ethical approval documents are listed in the appendices.
• Readers can find supporting evidence in the appendices.
• Each appendix focuses on a different experiment.

Books and Reports

• The report contains several appendixes.
• The instruction manual includes two appendixes.
• Extra diagrams are available in the appendixes.
• Financial records appear in the appendixes.
• Product specifications are included in the appendixes.

Everyday English

• Check the appendixes for additional details.
• The guidebook contains useful appendixes.
• We added new appendixes to the manual.
• Read the appendices before submitting your assignment.
• The book’s appendices explain technical terms in detail.

These examples show that both forms are correct, but appendices is generally the preferred choice in formal contexts.

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Words Similar to Appendix

If you’re writing professionally, you may also come across these related terms.

Word	Meaning
Supplement	Extra material added to a document
Annex	Additional section attached to a report
Addendum	Information added after completion
Attachment	A file or document included separately
Supporting Material	Extra information that supports the main content

Although these words are similar, they are not always interchangeable. An appendix usually contains supporting information that helps readers better understand the main text.

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Easy Trick to Remember Appendices or Appendixes

A simple memory trick can help you choose the correct form.

Memory Trick #1

Academic = Appendices

Both words sound more formal and are commonly used together.

Memory Trick #2

Think of the ending:

-ices = academic writing

Memory Trick #3

Remember this sentence:

Research papers use appendices. Everyday writing may use appendixes.

This simple rule works in almost every situation and helps you avoid confusion.

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Appendices vs Appendixes Comparison Table

The following table summarizes the key differences between the two plural forms.

Feature	Appendices	Appendixes
Grammar Type	Latin plural	English plural
Correctness	✅ Correct	✅ Correct
Meaning	Same	Same
Formality	High	Medium
Academic Writing	Preferred	Less common
Research Papers	Preferred	Rare
Professional Documents	Recommended	Acceptable
Everyday English	Common	More common
British English	Preferred	Accepted
American English	Preferred in formal writing	Common in informal writing
Best Choice	Academic and professional work	General and casual writing

The meaning never changes. Only the writing style and level of formality differ.

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FAQs

1. What is the plural of appendix?

Both appendices and appendixes are correct plural forms of appendix. The best choice depends on the context and writing style.

2. Which is correct: appendices or appendixes?

Both are grammatically correct. However, appendices is preferred in academic, scientific, and professional writing.

3. Is appendixes incorrect?

No. Appendixes is a valid English plural recognized by major dictionaries. It is simply less formal than appendices.

4. Which plural should I use in a thesis or dissertation?

Always choose appendices for academic work. It is the standard form used by universities, research institutions, and scholarly publishers.

5. Why are there two plural forms?

The word appendix comes from Latin. English kept the original Latin plural (appendices) while also developing a regular English plural (appendixes). Both eventually became accepted.

6. Can I use appendixes in formal writing?

Although it is grammatically correct, appendices is usually the better choice for formal reports, journal articles, and research papers.

7. Are appendices and appendixes interchangeable?

Yes. They have exactly the same meaning. The only difference is style and level of formality.

8. Which form is more professional?

Appendices is generally considered the more professional and academically appropriate form.

9. Does British English prefer appendices?

Yes. British English, especially in academic and professional contexts, usually prefers appendices.

10. Does American English use appendixes?

Yes. American English accepts both forms, although appendixes is more common in informal writing.

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Final Verdict

If you’ve ever been confused about whether to write appendices or appendixes, the answer is simple: both forms are correct. The difference lies in the context rather than grammar.

Choose appendices when writing:

• Research papers
• Theses
• Dissertations
• Scientific journals
• Legal documents
• Academic assignments
• Professional reports

Choose appendixes when writing:

• Blog posts
• Instruction manuals
• Informal reports
• Everyday English content

If you’re unsure which form to use, appendices is the safest option. It is widely accepted by universities, publishers, editors, and professional organizations, making your writing sound more polished and authoritative.

Understanding this small grammatical difference will help you write with greater confidence, maintain consistency, and communicate more professionally in both academic and everyday English.

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