Appendices or Appendixes: Which Plural Is Correct?

Appendices and appendixes are both correct plural forms of the word appendix, but they are used in different contexts.

Many writers become confused because English accepts two plural spellings, and dictionaries recognize both.

The confusion also comes from the word’s Latin origin and its modern English usage in books, medicine, education, and professional writing.

In this guide, you will learn the difference between appendices and appendixes, when each form is appropriate, how British and American English use them, common mistakes to avoid, practical examples, usage trends, and the best choice for your audience.

Quick Answer

Both appendices and appendixes are correct.

Appendices is the preferred plural when referring to extra sections at the end of books, reports, manuals, or research papers.
Appendixes is commonly used in medical writing when referring to more than one human appendix. Some style guides also accept it as the regular English plural.

Examples

✅ The report includes three appendices.

✅ The textbook has two detailed appendices.

✅ The surgeon studied several diseased appendixes.

✅ The hospital treated patients with infected appendixes.

The Origin of Appendices or Appendixes

The word appendix comes from the Latin word appendix, meaning “something attached” or “an addition.”

In Latin, many nouns ending in -ix formed their plural with -ices, which is why appendices became the traditional plural.

As English evolved, many Latin words adopted regular English plural forms by simply adding -es. That created appendixes.

Today, both forms are accepted.

Appendices keeps the traditional Latin plural.
Appendixes follows normal English grammar.

Because of this history, different fields prefer different versions.

Form	Origin	Common Use
Appendices	Latin plural	Books, reports, academic writing
Appendixes	English plural	Medicine and general English

British English vs American English Spelling

Both British and American English accept appendices and appendixes.

However, usage differs slightly.

British English often prefers appendices for formal writing.
American English also commonly uses appendices in publishing but accepts appendixes, especially in medical contexts.

Comparison Table

Context	British English	American English
Book sections	Appendices	Appendices
Academic papers	Appendices	Appendices
Medical writing	Appendixes or Appendices	Appendixes often preferred
General writing	Appendices	Either form

Which Spelling Should You Use?

Choose your spelling based on your audience.

Use Appendices if you are writing:

Academic papers
Research articles
Books
Business reports
Government documents
Educational material

Use Appendixes if you are writing:

Medical documents
Health articles
Clinical reports
When following a style guide that prefers regular English plurals

For global audiences

Appendices is usually the safest choice because it is more widely recognized in formal writing.

Common Mistakes with Appendices or Appendixes

Here are mistakes writers often make.

Incorrect	Correct
The book has two appendix.	The book has two appendices.
The report includes many appendixs.	The report includes many appendices.
Three appendixes are attached to the textbook.	Three appendices are attached to the textbook.
The doctors removed several appendices.	The doctors removed several appendixes. (medical context)

Tips

Use appendices for documents.
Use appendixes mainly for anatomy.
Stay consistent throughout your writing.

Appendices or Appendixes in Everyday Examples

Email

Please see the appendices for additional financial data.

News

The investigation included several appendices with supporting evidence.

Social Media

The guide now includes two helpful appendices for beginners.

Academic Writing

The full survey appears in Appendix A, while supporting tables are found in the appendices.

Medical Writing

Researchers examined inflamed appendixes from several patients.

Business Report

The final appendices contain charts and technical notes.

Appendices or Appendixes – Google Trends & Usage Data

Search data shows that appendices is much more popular than appendixes.

Usage by Country

Country	Preferred Form
United Kingdom	Appendices
United States	Appendices (general), Appendixes (medical)
Canada	Appendices
Australia	Appendices
New Zealand	Appendices

Usage by Context

Context	Preferred Form
Books	Appendices
Research	Appendices
Education	Appendices
Government	Appendices
Medicine	Appendixes

Overall, appendices dominates search results because it is widely used in publishing and education.

Comparison Table

Word	Correct	Primary Use
Appendix	✅	Singular
Appendices	✅	Books, reports, academic writing
Appendixes	✅	Medical writing, regular English plural
Appendixs	❌	Incorrect spelling

FAQs

Is appendices correct?

Yes. Appendices is the standard plural for book and report sections.

Is appendixes also correct?

Yes. Appendixes is also correct and is often used in medical contexts.

Which plural is more common?

Appendices is much more common in publishing, education, and formal writing.

Do British and American English use different forms?

Both accept both spellings, but appendices is preferred in most formal writing.

Which should students use?

Students should normally use appendices in essays, dissertations, and research papers.

Is appendixs a word?

No. Appendixs is incorrect.

Why are there two plural forms?

Because appendices comes from Latin, while appendixes follows modern English plural rules.

Conclusion

Both appendices and appendixes are correct, but the right choice depends on the context: use appendices for books, reports, and academic writing, and appendixes mainly for medical references. Following this simple rule will help you write more accurately and professionally.

When in doubt, choose appendices, as it is the most widely accepted form in formal English.

To strengthen your grammar further, you may also enjoy reading our related guide on buses or busses, which explains another common plural spelling question and helps improve everyday writing confidence.