Appendixes vs Appendices: Which Plural Is Correct?

Both plurals are correct, and the choice often comes down to context. Appendices is the more traditional, Latin-derived plural and remains common for the sections at the end of a book or document, while appendixes is increasingly used, especially in American English, for both the body part and the document sections alike.

The Short Answer at a Glance

Form	Status	What it does	Example
appendices	Traditional, widely used	Plural of appendix, especially for document sections	The report includes three appendices with supporting data.
appendixes	Increasingly common, especially in American usage	Identical meaning; also common for the body part	The report includes three appendixes with supporting data.

Both forms are listed in major dictionaries. Appendices leans more traditional and academic, while appendixes has become more common in everyday American writing and especially in medical contexts referring to the body part.

What Appendices Means and How It Works

Appendices is a plural form of appendix, a noun referring to a supplementary section added to the end of a book, report, or document, typically containing supporting material like data tables, charts, source documents, or additional explanations that would interrupt the main text if placed earlier.

The word appendix itself comes from Latin, and appendices represents the traditional Latin-style plural, formed the same way other Latin-derived words sometimes keep their original plural patterns in English, such as index becoming indices in certain contexts, or matrix becoming matrices.

Grammatically, appendices functions as a standard plural noun: the appendices, several appendices, three appendices at the end of the manuscript. It pairs with plural verbs and determiners just like any other regular plural: “the appendices include,” not “the appendices includes.”

Appendices has long been the more common plural specifically when referring to the sections of a document, particularly in academic, legal, and technical writing, where tradition and formality often favor this Latin-style ending.

What Appendixes Means and How It Works

Appendixes means exactly the same thing as appendices when referring to document sections: supplementary material placed at the end of a book, report, or paper. It also serves as the plural for appendix in its anatomical sense, referring to the small, finger-shaped pouch attached to the large intestine.

The key difference is that appendixes follows the regular English pattern for forming plurals, simply adding “es” to the base word, the same way “box” becomes “boxes” or “fox” becomes “foxes.” This is part of a broader, long-running pattern in English where originally Latin or Greek-derived words gradually shift toward standard English plural endings over time, even while the older, original-language plural remains in use alongside it.

In medical and anatomical writing specifically, appendixes has become the dominant plural form when referring to the body part, since medical literature has largely moved toward the standard English plural in this context, even though appendices technically remains an available, dictionary-recognized alternative there as well.

Grammatically, appendixes behaves identically to appendices in every respect, functioning as a standard plural noun in all the same sentence structures.

Appendixes vs Appendices: Key Differences Side by Side

Feature	Appendices	Appendixes
Part of speech	Plural noun	Plural noun
Core meaning	Supplementary document sections; also the body part	Identical meaning
Typical use	Academic, legal, and technical writing (document sections)	Medical writing (body part); increasingly common for document sections too
Register	Traditional, formal	Standard, increasingly common across registers
Example	The dissertation’s appendices span nearly fifty pages.	The surgeon has removed several appendixes over the years.

What the table can’t fully capture is how genuinely split usage remains depending on context. For document sections, appendices still holds a slight edge in formal and academic writing, while appendixes has become the clearer favorite specifically when discussing the anatomical organ, particularly in modern medical literature.

Correct Examples in Real-Life Contexts

Everyday speech

• The user manual has like five appendices just for troubleshooting steps.
• My doctor said some people live their whole lives without their appendixes ever causing problems.
• I always skip straight to the appendices when I’m looking for the reference tables.
• Two of my cousins have had their appendixes removed, which seems like a lot for one family.

Workplace writing

• Please attach the budget breakdown as one of the report’s appendices.
• The compliance document includes three appendixes covering regional regulations.
• Our style guide recommends using “appendices” consistently throughout all formal reports.
• The technical manual’s appendixes list every error code and its corresponding fix.

Texting

• ugh this textbook has so many appendices I don’t even know where to start
• just found out my friend’s appendix burst, she’s getting her appendixes out tomorrow lol typo but you get it

School and academic

• The dissertation’s appendices include full transcripts of every interview conducted.
• Students are required to cite all data sources used in the appendices.
• The biology textbook’s appendices cover supplementary diagrams not included in the main chapters.
• Her thesis committee asked for additional appendices documenting the raw survey data.

Formal writing

• The contract’s appendices outline specific terms not covered in the main agreement.
• Medical records indicated that both patients had healthy appendixes prior to surgery.
• The environmental impact report’s appendices contain the full technical assessments.
• Surgeons noted that ruptured appendixes require immediate medical attention.

Common Mistakes People Make (and How to Catch Them)

Assuming only one plural is correct

Wrong assumption: Appendixes is simply a misspelling of appendices, or vice versa. Right understanding: Both plurals are recognized in major dictionaries, with usage varying somewhat by context and register.

This isn’t a genuine sentence-level error, but a common misunderstanding, since many English speakers assume Latin-derived plurals have only one “correct” form, when in fact several such words have shifted toward standard English plurals over time.

Inconsistent use within the same document

Wrong: The report refers to appendices in the table of contents but appendixes throughout the body text. Right: The report consistently uses one plural form throughout.

Since both forms are accepted, the real risk is inconsistency rather than outright error, and switching between them mid-document tends to look like a proofreading oversight.

Using appendices exclusively for the anatomical organ without checking context

Less common in modern usage: Several appendices were removed during that surgical rotation. More common in modern usage: Several appendixes were removed during that surgical rotation.

While appendices remains technically acceptable for the body part, appendixes has become the more frequently used and expected form in contemporary medical writing specifically.

Overcorrecting a style guide’s preference into a universal rule

Wrong assumption: Since my school’s style guide prefers appendices, appendixes must always be incorrect. Right understanding: A specific style guide’s preference reflects that guide’s own standard, not a universal rule that applies to all writing everywhere.

Individual publications, academic institutions, and organizations often have their own established preference, but that doesn’t mean the other form is wrong elsewhere.

A Fast Trick to Choose the Right One

For document sections, especially in academic, legal, or formal writing, appendices remains the safer, more traditional default, particularly if you’re following an established style guide that doesn’t specify otherwise. For references to the anatomical organ, appendixes has become the more commonly expected and modern choice, especially in medical writing.

A simple context check: ask whether you’re writing about a book’s or report’s supplementary sections, or about the body part. That single distinction often points you toward the more statistically common choice in each specific context, even though both plurals remain technically valid either way.

This trick works well as a general guideline, but it has a real limit: usage is genuinely split and evolving, so checking your specific publication’s or institution’s style guide remains the most reliable way to confirm which form is expected in your particular context.

How They Sound in Real Situations

A text exchange

Priya: Did you finish the report?

Sam: Almost, just need to finalize the appendices with the budget tables.

Priya: Perfect, send it over when you’re done.

Appendices works naturally here, reflecting common usage for document sections in a workplace context.

A workplace email

Subject: Final review before submission

Hi team,

Before we submit the grant proposal, could someone double-check that all referenced data appears correctly in the appendixes? I noticed a formatting inconsistency in the third one.

Thanks, Marcus

Appendixes works comfortably here too, since both forms are accepted for document sections, and this choice may simply reflect the writer’s personal or organizational preference.

An article-style excerpt

Surgeons removed both patients’ appendixes during the same emergency shift, a rare coincidence that hospital staff said they’d never experienced before. Both procedures were completed without complications.

Appendixes is correct and more typical here, reflecting standard modern usage when referring to the anatomical organ.

Formal Writing vs Casual Writing

Both plurals are acceptable across formal and casual writing, so this isn’t strictly a matter of register. What matters more is context and, in formal settings, adherence to an established style guide. Academic, legal, and technical writing has traditionally leaned toward appendices for document sections, while modern medical writing has shifted more toward appendixes for the anatomical organ.

In casual speech and everyday writing, both forms circulate without much friction, and most readers won’t notice or mind which one you choose, since the meaning remains perfectly clear either way.

Neither AP nor Chicago style enforces one plural exclusively, though Chicago has historically shown some preference for appendixes in general use, while many academic and legal style guides continue to favor appendices, particularly for document sections.

Related Mix-Ups People Also Search For

Index vs Indexes vs Indices

This closely related word follows a similar pattern, with indices representing the traditional Latin-style plural and indexes representing the standard English plural, both accepted depending on context, particularly in mathematics and technical writing versus everyday use. Example: The book’s indexes are straightforward, but the mathematical indices in chapter seven require careful attention.

Appendix vs Addendum

These two are related but distinct. An appendix is a supplementary section included as part of the original document’s structure, while an addendum is something added afterward, often to update or correct the original material. Example: The appendices were part of the original report, while the addendum was issued separately after an error was discovered.

Matrix vs Matrixes vs Matrices

Another Latin-derived word with a similar dual-plural pattern, where matrices remains common in mathematics and technical fields, while matrixes appears more rarely but is still recognized in some contexts. Example: The textbook’s appendices include several matrices used throughout the statistics chapters.

Quick Practice: Test Yourself

Both forms are acceptable in each of these sentences; choose whichever fits the typical context described.

1. A legal contract’s supplementary sections are referred to as the agreement’s ______. (appendices / appendixes)
2. A medical journal article discusses complications involving patients’ ______. (appendices / appendixes)
3. An academic dissertation includes several ______ with raw survey data. (appendices / appendixes)
4. A hospital’s surgical records note that both ______ were removed successfully. (appendices / appendixes)
5. A technical manual’s ______ list troubleshooting steps for common errors. (appendices / appendixes)
6. A biology textbook’s supplementary chapters are labeled as ______ throughout. (appendices / appendixes)

Answer Key

1. appendices: matches the traditional, more common choice for formal legal document sections.
2. appendixes: matches the more common modern choice for the anatomical organ in medical writing.
3. appendices: matches typical academic convention for document sections, though appendixes would also work.
4. appendixes: matches standard modern medical usage for the body part.
5. appendices: fits traditional technical writing convention, though appendixes remains acceptable.
6. appendices: matches common academic textbook convention for document sections.

Frequently Asked Questions

Is appendixes or appendices the correct plural of appendix?

Both are correct. Appendices is the traditional Latin-style plural, often used for document sections, while appendixes follows the standard English plural pattern and has become especially common when referring to the anatomical organ.

Which plural should I use when referring to sections in a report or book?

Appendices remains the more traditional and commonly expected choice for document sections, particularly in academic and formal writing, though appendixes is increasingly used in that context as well.

Which plural is used in medical writing?

Appendixes has become the more commonly used plural in modern medical writing when referring to the anatomical organ, though appendices remains a recognized, if less common, alternative there too.

Is one plural considered more correct than the other?

No. Neither plural is more accurate or more official than the other. The choice largely reflects context, tradition, and which specific style guide, if any, a writer is following.

Do style guides have a strict rule about which plural to use?

Not universally. Some academic and legal style guides favor appendices, particularly for document sections, while others, including some general style guides, lean toward appendixes, so checking your specific publication’s preference is the most reliable approach.

Can I use appendixes and appendices interchangeably in the same document?

It’s best to choose one and use it consistently throughout a single document, since mixing the two can look inconsistent even though both are individually correct.