Appendices or Appendixes? Clarifying Usage

When I was editing my first academic paper, I remember how puzzled I felt trying to decide whether to write appendices or appendixes.

That moment pushed me to really dive deep into the language, the rules, and even the historical origins of both terms. What I found was not only fascinating but incredibly practical, especially for anyone working in English writing or research.

Let’s demystify this a bit. Both forms—appendices and appendixes—are correct. However, APA style and many academic communities tend to prefer appendices. The key here is consistency.

If you’re writing a paper, choose one and stick with it throughout. You may wondered which one is more common—appendices often takes the lead in formal contexts. Yet, in general use, either can be acceptable, depending on your preferences or the context you’re working in.

So, how do you figure out what’s best? Think about the style guide you’re using. Are you following APA, or a different academic standard? Also, get familiar with your audience.

If you’re writing for scholars, consistency and formal tone are crucial. But in less formal settings, such as blogs or casual articles, you’ll often seen both spellings used interchangeably. Use what fits the tone and purpose of your work.

Having encountered this confusion myself, I now say with confidence: choosing between appendices and appendixes isn’t about right or wrong—it’s about clarity, context, and knowing the rules.

If you ever wondered which is correct, you’re not alone. We’ll break it down together, with sense, a little history, and common-sense thinking.

Table of Contents

What do “Appendices” and “Appendixes” Mean?

When I first started writing academic documents, I often came across the terms appendices and appendixes.

At first, I didn’t fully understand what they meant or how they were used, but with time and experience, I began to explore their meanings more deeply. Both words are plurals of appendix, a term that can refer to something attached at the end of a book or document.

These sections usually provide extra or supplementary information to help readers better understand the main content. In this context, it’s important to stay consistent, especially when working on a formal piece of writing.

The word appendix can also have a very different meaning in an anatomical sense.

In the human body, it’s a small, tube-shaped sac attached to the large intestine—quite a contrast from its literary use. Depending on the context, the idea of an appendix may represent a part of the body or a section in a report.

Let’s not forget how versatility plays a core role here. Whether you are talking about a primary source in a research paper or referencing an additional organ in the body, both meanings are valid.

So, the next time you see either word, think of its defined role in the literary or anatomical world—and choose based on its context.

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Singular of “Appendices” or “Appendixes”

When you’re reading a book, report, or academic document, you may come across sections at the end filled with extra information, references, or details.

These are often labeled as appendices or appendixes, but what is the singular form of these words? Simply put, it’s appendix.

This term is commonly used in both formal and informal writing to denote a section that is appended to the main text to provide support or enhance the reader’s understanding of the content.

As someone who’s worked with research writing, I’ve often seen the appendix serve different purposes depending on the contexts. In a formal academic report, an appendix might include additional material such as charts, references, or background information.

But the word also has a second meaning in anatomy—a specific organ that’s attached to the large intestine, known as a tube-shaped sac. This dual meaning shows how versatile the word appendix is in both scientific and educational fields.

Whether you’re working on a project or studying human biology, knowing when and how to use appendix, appendices, or appendixes makes your writing clearer and more precise.

Why both “Appendices” and “Appendixes” are the Plurals of ‘Appendix’?

When I first started editing academic texts, I noticed something curious: some writers used appendices, while others preferred appendixes. This made me pause and see how English handles such variations.

As it turns out, the word “appendix” is unique because it has two acceptable plurals—appendices and appendixes. That’s not a mistake; it’s actually a great example of how the language allows flexibility depending on the style, context, and rules you’re following.

The form appendices is derived from Latin, where words with certain endings take an “-ices” pattern in the plural. On the other hand, appendixes follows regular English pluralization—where you simply add “-es” for nouns ending in “x.”

So, both are used, and it really just depends on the guide or style you prefer. Over time, this dual usage has become standard. In academic writing, I’ve often seen authors follow what the APA or other manuals considered correct.

But whether it’s formal or informal, this case shows how the word “appendix” has forms that happen to co-exist.

It’s fascinating how the root of a word can influence its plural, especially when it’s being used across different contexts.

You might wonder how such exceptions work, but once you follow the style you’re used to, it all makes sense. So, whether you’re adding just one appendix, or several appendices/appendixes, what matters is that your choice is backed by a consistent rule, and it fits the form of your writing.

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“Appendices” or “Appendixes”: Where to use which one?

When we discuss the word “appendix”, it’s important to know how its plural forms are used in different contexts. From my own academic writing and teaching experience, I’ve noticed how people often get confused between “Appendices” and “Appendixes”.

The choice depends on what you’re referring to. If you’re talking about anatomy, like the small, pouch-shaped organ attached to the large intestine, then the correct form is “Appendixes”. This follows the English pluralization pattern and is specifically meant for use in medical or biological references.

On the other hand, if you’re working with a document, book, or academic report, you should use “Appendices”. These are sections usually added at the end of a text to provide extra information, details, or support for the main content.

These may include charts, references, or other materials that clarify or extend the primary discussion. Because “Appendices” follows the Latin-origin pattern, it’s the standard in more formal and scholarly writing.

It’s useful to note that the words come from different patterns, and keeping that in mind helps in choosing the respective usage. In essence, understanding the plural forms and how they’re used differently makes your writing clearer and more correct.

Examples in Context

Appendix: (Singular)

The appendix at the end of the report includes the full survey results.
My biology textbook has an appendix that lists all the scientific names.
The surgeon removed her appendix after it became inflamed.
You can check Appendix B for the complete financial breakdown.
His pain was caused by an infected appendix, requiring immediate surgery.
The appendix provides definitions for technical terms used in the main text.
In human anatomy, the appendix is attached to the large intestine.
I added an appendix to my essay to include extra data without crowding the main section.

Appendices (Plural in Reference to a Book or Document)

The appendices contain charts and graphs that support the findings in the main chapters.
All legal terms are explained in the appendices at the back of the contract.
The research paper includes three appendices to present raw data and additional notes.
Please refer to the appendices for a full list of references and citations.
In academic writing, appendices are often used to include supplementary materials.
Her thesis had several appendices that provided detailed experimental results.
The report’s appendices helped clarify complex statistics for the readers.
You’ll find the detailed methodology in the appendices, not in the main text.

Appendices (Plural in Reference to Anatomy)

In rare cases, people are born with appendices on both sides of the abdomen.
The surgeon noted that the patient had two inflamed appendices, an unusual condition.
Medical studies have documented duplicate appendices in some individuals.
During the autopsy, the pathologist discovered multiple appendices attached to the intestine.
Some animals naturally have multiple appendices for digestive functions.
The research focused on congenital anomalies involving duplicated appendices.
The presence of two appendices was confirmed through abdominal imaging.
These rare cases of dual appendices are often found accidentally during surgery.

Frequently Asked Questions

Is one form more correct than the other?

Both “appendices” and “appendixes” are correct plural forms of “appendix”, but their usage depends on context and preference:

“Appendices” is the Latin plural and is often preferred in formal writing, especially when referring to books, documents, or academic materials.
- Example: The report includes several appendices detailing the data.
“Appendixes” is the English plural, more commonly used when referring to the anatomical organ.
- Example: Some rare medical cases report people with two appendixes.

Are there regional preferences between “appendices or appendixes”?

Yes, there are regional preferences between “appendices” and “appendixes”, though both are grammatically correct:

In British English, “appendices” is more commonly used for both contexts — whether referring to books/documents or anatomy. The Latin plural form is generally favored.
In American English, there’s a bit more flexibility:
- “Appendices” is still the go-to for documents or reports.
- “Appendixes” is often preferred when referring to the anatomical organ (like the appendix in your body).

In summary:

British English: Mostly uses appendices across contexts.
American English: Uses appendices for documents and appendixes for anatomy.

Do academic style guides prefer one form?

Yes, academic style guides often prefer one form over the other, depending on the context and the guide itself:

Chicago Manual of Style and APA Style (commonly used in academic writing) prefer “appendices” when referring to additional material in books, theses, or reports. This aligns with the traditional Latin plural form.
For anatomical references, medical and scientific writing may use “appendixes”, but some still stick with “appendices”, especially in British publications.

Quick Guide:

Academic documents (reports, theses, papers) → ✅ Appendices
Scientific/anatomical contexts → Depends, but Appendixes is accepted

So, while both forms are correct, “appendices” is more widely accepted in academic and formal writing for supplementary content.

A Final Look at “Appendices” or “Appendixes”

Looking back at the difference between Appendices and Appendixes, I’ve found that understanding the context really helps.

In my academic writing, when I needed to add additional materials at the end of books, reports, or documents, the word Appendices was always the right fit. This follows the Latin pluralization pattern, which is often used in formal settings and matches the style of many scholarly discussions.

The sections labeled as appendices often include terms, charts, or extra content that supports the main work. For anyone looking to write with consistency and avoid common mistakes, it’s essential to consider the audience and the nature of the work being done.

On the other hand, when I’ve had conversations in science classes about the human body, the word Appendixes always came up. This refers to the anatomical organ, a small, pouch-shaped structure attached to the large intestine.

Unlike the Latin form, this follows English rules of pluralization, which makes it easier to use when talking about biology or anatomy. If you’re still unsure, a quick recap is that it all depends on your topic. A solid understanding of these nuances will help you use both forms confidently, reduce doubts, and ensure your usage stays accurate.

Ronnie Dawson

A communication coach with a background in public speaking and business English. He helps professionals refine their English for workplace success.