Appendices vs. Appendixes: Which Spelling Is Correct?

Appendices vs. Appendixes: Which Spelling Is Correct? explains why both plural forms are accepted and how context helps you choose the right one.

The short answer is that appendices and appendixes are both correct plural forms of appendix. Both spellings appear in real texts, dictionaries, and formal writing. However, the preferred plural has varied across different contexts. Historically, older real texts favored appendices, especially in the literary sense and medical sense. About 150 years ago, a dictionary might have recommended this form, but modern English recognizes both forms. The American Heritage Dictionary of the English Language offers a helpful reference for students, professionals, and writers researching this grammar issue. If you’re stuck asking, “Wait, which one is right?” consider the word’s meanings, actual usage, and surrounding context instead of assuming one spelling is always correct. These simple explanations can clear your confusion and make choosing a spelling feel more confident and stress-free.

The difference becomes clearer when you examine foreign-derived words and their plural endings. Over time, English has Anglicized many words while retaining some original forms. For example, English dictionaries recognize gymnasiums and gymnasia, memorandums and memoranda, syllabuses and syllabi, and cactuses and cacti. This linguistic development explains why appendices and appendixes both exist. One follows a traditional plural pattern, while the other follows the regular English plural pattern by adding -es. In academic writing, publishing, reports, research papers, books, and formal documentation, appendices remains a traditional and common choice for supplementary sections at the end of books and other documents. In contrast, appendixes is also technically correct and appears in document-related writing and anatomical writing. For example, a doctor discussing the anatomical appendix may use either accepted form, depending on the style and subject. Both terms can describe additional sections in documents or anatomical structures involving people and medicine.

A practical guide to correct usage starts with checking the style rules of your institution, publisher, or project. Choose one form and use it consistently throughout your work. One of the common errors is to switch between appendices and appendixes in different sections without realizing it, creating inconsistency in otherwise clear writing. A reliable approach is to review your documents before submission and correct mistakes whenever you find them. This simple habit can reduce inconsistency in real-world applications and make your work easier to follow. You don’t need complicated grammar rules to make the right choice. Instead, use practical examples to understand when to use each form and avoid unnecessary confusion. Once you recognize the pattern, the decision should feel simple. Although soothe and digestion have no direct connection to this spelling question, they remind us to check the meaning of individual words before using them in a sentence.

Quick Answer

Appendices and appendixes are both correct. Each is the plural of appendix, a word that can refer to supplementary material at the end of a document or a small organ attached to the large intestine.

• Appendices: A familiar choice in academic papers, dissertations, books, and formal reports.
• Appendixes: A valid alternative that follows the regular English plural pattern. It is also commonly used when referring to the anatomical structures.
• Appendix: The singular form, used when referring to one supplementary section or one anatomical structure.

For example:

• “The research paper includes three appendices with supporting data.”
• “The revised handbook contains two appendixes.”
• “The surgeon explained the function of the appendix.”

If you’re writing a formal academic paper and your style guide doesn’t specify a preference, appendices is a sensible default. However, you won’t be making a spelling mistake by choosing appendixes.

Comparison Overview

The following table highlights the main differences between appendices and appendixes.

Feature	Appendices	Appendixes
Singular form	Appendix	Appendix
Grammatical number	Plural	Plural
Is it correct?	Yes	Yes
Word formation	Traditional Latin-derived plural	Regular English plural
Common document-related use	Research papers, theses, books, and reports	General writing and some publications
Anatomical use	Possible, but less usual	Commonly used
Meaning	More than one appendix	More than one appendix
Best approach	Follow your style guide	Follow your style guide

The important point is that the two spellings can have the same meaning when they refer to supplementary sections in a document. Neither form automatically makes a sentence more grammatical or more professional.

Context still matters. Academic writers often prefer appendices, while appendixes offers a straightforward alternative. When writing about the human body, appendixes is generally the more familiar choice.

What Does Appendix Mean?

The word appendix has two main meanings. It can describe extra material attached to a written work or a small anatomical structure in the human body. Understanding these meanings helps you choose the most natural plural form.

Appendix as a Supplementary Section in a Book or Document

In writing, an appendix is a section at the end of a book, report, thesis, or other document that provides additional information. It allows authors to include useful details without interrupting the main discussion.

Imagine writing a research paper about customer satisfaction. Your main text explains the findings, but readers may also want to see the complete questionnaire and detailed survey results. Instead of squeezing everything into the main chapters, you can place those materials in an appendix.

Common materials included in an appendix are:

• Questionnaires and surveys: The questions researchers asked participants.
• Supporting data: Detailed tables, measurements, or additional results.
• Technical explanations: Formulas, calculations, or procedures that need more space.
• Supplementary documents: Relevant forms, sample materials, or additional records.
• Extended examples: Extra illustrations that support the main discussion.

For example:

The report includes an appendix containing the complete survey questionnaire.

If a report contains several supplementary sections, you can write:

The report includes three appendices covering survey methods, raw data, and additional calculations.

You could also use appendixes in the second sentence. Both forms are acceptable for this meaning, although appendices is a familiar choice in formal and academic writing. Cambridge Dictionary lists both plural forms for the document-related meaning.

Appendix as a Part of the Human Body

In anatomy, the appendix is a small, pouch-like structure connected to the large intestine. It sits in the lower-right area of the abdomen and can become inflamed, a condition called appendicitis.

The plural generally used for this body part is appendixes. The distinction matters because dictionaries commonly associate appendices with supplementary sections and appendixes with anatomical structures.

Consider these examples:

• “The patient underwent surgery to remove an inflamed appendix.”
• “The medical textbook discusses diseases affecting the appendixes.”
• “The researchers examined the appendixes in the animal specimens.”

The singular appendix works when you mean one structure. When referring to multiple structures, appendixes is the usual choice.

This usage doesn’t mean appendices is an incorrect word. It simply reflects the established preference for a particular meaning.

Why Does Appendix Have Two Plural Forms?

English has borrowed many words from Latin and other languages. Some borrowed words retain traditional plural patterns, while others gradually adopt the ordinary English rules.

The word appendix follows both patterns:

• Appendix → appendices: A traditional Latin-derived plural.
• Appendix → appendixes: A regular English plural formed by adding -es.

The same general pattern appears in other English words with Latin origins. For example, index has the plurals indices and indexes, although their preferred uses can vary by context.

English doesn’t require every borrowed word to follow only its original language’s grammar. Over time, speakers and writers adopt forms that fit English usage.

That is why you can encounter both appendices and appendixes in dictionaries and published writing. The two forms are established alternatives, not a correct spelling and a misspelling.

Main Differences Between Appendices and Appendixes

Although the words share the same singular form, their typical contexts aren’t identical. Understanding these preferences will help you choose a form that sounds natural to your readers.

Appendices Is Common in Academic and Formal Writing

When you write a thesis, dissertation, research paper, or detailed report, appendices is a familiar plural choice. It fits the traditional style often used for supplementary sections in formal documents.

For instance, a research paper might include:

• Appendix A: Survey Questionnaire
• Appendix B: Additional Statistical Results
• Appendix C: Interview Questions

When referring to all three sections together, you could write, “The appendices provide additional details about the research methods.”

This wording is clear and conventional. Readers can recognize that the sections contain supporting material rather than the main argument.

Appendices also appears in books, legal documents, and technical reports. However, the spelling alone doesn’t determine whether a document is formal. The organization, language, and formatting matter too.

Use appendices when it matches your chosen style guide or the terminology already used in your document.

Appendixes Follows the Regular English Plural Pattern

The word appendixes follows a straightforward English spelling rule: add -es to the singular noun appendix.

This pattern makes the plural easy to form without relying on a traditional Latin ending. It also appears in dictionaries as an accepted form for supplementary sections.

Consider these sentences:

• “The manual contains several appendixes with troubleshooting instructions.”
• “The editor revised the appendixes before publishing the book.”
• “Each of the appendixes covers a separate topic.”

All three sentences use appendixes correctly.

The form can be especially useful in online documentation. For example, a software website might organize several independent topics under a heading called “Appendixes,” with each topic linking to its own page.

The Chicago Manual of Style discusses this exact type of organizational choice. Its guidance explains that writers can use a collective heading or separate appendix pages depending on how they arrange the material.

The important lesson is simple: regular English pluralization is not a sign of poor grammar. You can use appendixes without worrying that you’ve made a spelling error.

Which Form Is More Appropriate for a Research Paper?

For most research papers, appendices is a sensible default when your institution or publisher doesn’t specify a different form.

Why? The word is widely recognized in academic contexts, and it fits the traditional terminology used for supplementary sections.

However, your institution’s requirements take priority over general preferences. A journal may have its own editorial rules, while a university may provide a thesis template with predefined appendix headings.

Before submitting your work, check:

• Your university’s thesis or dissertation handbook.
• The journal’s instructions for authors.
• Your department’s writing guidelines.
• The style guide required for the assignment.
• Any template supplied by your editor or instructor.

If the document already uses appendixes consistently and no applicable rule requires appendices, there’s generally no reason to change every instance simply because another form is more familiar.

The best choice is the one that meets the relevant requirements and stays consistent throughout the document.

Are Appendices and Appendixes Interchangeable?

For supplementary sections in a document, yes. Both plural forms are accepted.

You can write:

• “The appendices contain the supporting evidence.”
• “The appendixes contain the supporting evidence.”

Both sentences communicate the same idea. The difference is spelling preference, not meaning.

The distinction becomes more useful when the word refers to the body part. In that context, appendixes is the usual plural form according to major learner’s dictionaries.

Here’s a practical comparison:

Context	Natural choice	Reason
University dissertation	Appendices	Familiar academic convention
Research report	Appendices	Common formal usage
General document	Appendices or appendixes	Both are accepted
Online reference material	Appendixes or appendices	Depends on the site’s editorial choices
Medical discussion of multiple anatomical structures	Appendixes	Usual plural for the body-part meaning

These are usage preferences, not absolute rules for every publication. A dictionary’s preferred form can guide you, but a specific style guide may make a different choice.

Read More:Hustle vs Hussle: Which Spelling Is Correct?

Appendices vs. Appendixes Examples in Sentences

Examples make the distinction easier to remember. The following sentences show how each form works in everyday, academic, professional, and medical writing.

Examples Using Appendices

Use appendices when referring to supplementary sections in a document, especially when that form matches your style guide.

• Academic research: “The appendices contain the survey questions and supplementary data collected during the study.”
• Business reporting: “Please review the appendices for the detailed financial tables supporting our annual report.”
• Book publishing: “The appendices provide additional background on the historical events discussed in the final chapter.”
• Legal documentation: “The contract includes appendices listing the supporting schedules and related information.”
• Education: “The professor asked students to consult the appendices before submitting their research papers.”
• Technical writing: “The manual’s appendices contain reference charts, configuration details, and troubleshooting information.”
• Scientific research: “The appendices explain the experimental procedures and provide additional results.”

Notice the shared purpose: each sentence refers to extra information that supports a larger written work.

For example, a scientific paper might summarize its findings in the main text and place lengthy data tables in its appendices. Readers who want more detail can consult those sections without losing track of the main argument.

Examples Using Appendixes

Appendixes works when referring to supplementary document sections and is the usual plural for the anatomical meaning.

Here are examples of its use:

• General writing: “The handbook contains several appendixes with additional reference material.”
• Document preparation: “The editor reorganized the appendixes to make the report easier to navigate.”
• Online documentation: “The website’s appendixes cover separate technical topics.”
• Anatomy: “The textbook discusses conditions affecting the appendixes.”
• Medical research: “The researchers compared the appendixes of the specimens.”
• Publishing: “The author added two appendixes to the revised edition.”

The first three sentences use appendixes to mean supplementary sections. The remaining examples refer to anatomical structures.

That difference is worth remembering: the meaning of the word can influence which plural form sounds most natural.

Incorrect or Awkward Uses to Avoid

Both spellings are correct, but writers can still make mistakes when using them.

Mistake: Incorrect subject-verb agreement

Incorrect: “The appendices contains the survey results.”

Correct: “The appendices contain the survey results.”

The subject is plural, so the verb must also take its plural form.

Mistake: Using the wrong singular or plural form

Incorrect: “The appendix contain several tables.”

Correct: “The appendix contains several tables.”

When you’re talking about one appendix, use the singular verb contains. When you’re talking about multiple appendices, use contain.

Mistake: Writing an unaccepted plural spelling

Incorrect: “The appendixs contain additional information.”

Correct: “The appendices contain additional information.”

You can also write, “The appendixes contain additional information.” The form appendixs doesn’t follow either accepted plural pattern.

Mistake: Switching spellings without a reason

Awkward: “See the appendices for the survey results. The appendixes also include the interview questions.”

Better: “See the appendices for the survey results and interview questions.”

Switching between the two forms isn’t automatically a grammatical error. However, using one form consistently makes a document easier to edit and read.

How to Choose Between Appendices and Appendixes

Choosing the right spelling is easier when you consider the context rather than relying on a rule that says one form is always correct.

Consider Your Audience and Purpose

Think about who will read your document and what kind of writing you’re producing.

If you’re preparing a university dissertation, a research paper, or a formal business report, appendices is a practical starting point. It is familiar in academic and professional contexts.

For general writing, appendixes is also acceptable. You don’t need to avoid it simply because it follows the regular English plural pattern.

When discussing anatomical structures, choose appendixes unless your medical reference or editorial guidelines specify otherwise.

For example:

• A student might write, “The appendices contain the interview transcripts.”
• A software writer might write, “The appendixes explain the advanced configuration options.”
• A medical author might write, “The study examines abnormalities affecting the appendixes.”

Each example uses a plural form that fits its context.

Follow Your Style Guide

A style guide helps writers make consistent decisions about spelling, punctuation, capitalization, headings, and document structure.

If your work must follow a particular style guide, use its recommendations instead of relying solely on personal preference.

Useful resources include:

• Cambridge Dictionary — explains the word’s meanings and plural forms.
• Oxford Learner’s Dictionaries — distinguishes the usual plural forms for anatomical and document-related meanings.
• The Chicago Manual of Style — provides guidance on manuscript preparation and appendix organization.

These sources are particularly useful because they show how context affects actual usage. Oxford, for example, identifies appendixes as the usual plural for the body part and appendices as the usual plural for a section in a book or document.

Oxford Learner’s Dictionaries

If you’re writing for a university or publisher, also check its official submission instructions. A general dictionary cannot replace a specific requirement.

Keep Your Spelling Consistent

Consistency matters more than repeatedly debating which accepted form is better.

Suppose your report has three supplementary sections. You label them Appendix A, Appendix B, and Appendix C. When referring to all three together, use the plural form you’ve chosen for the document.

For example:

• “See the appendices for additional calculations.”
• “The appendices provide supporting evidence for the report’s conclusions.”

If your publication uses appendixes, maintain that choice instead.

Check the following places during editing:

• Section headings and appendix titles.
• The table of contents.
• Cross-references within the main text.
• Captions and notes.
• The index, if the document includes one.

A quick search for both spellings can help you spot accidental inconsistencies before submission.

How to Use Appendices in Academic Papers and Reports

Understanding the plural spelling is useful, but knowing how appendices function in a document helps you use the word correctly.

When Should You Include an Appendix?

An appendix is useful when readers may need additional information but don’t need to see it in the main discussion.

For example, a researcher studying online shopping habits might discuss the study’s main findings in the paper. The complete questionnaire, extended statistical tables, and detailed methodology could go in supplementary sections.

Common reasons to include an appendix are:

• To provide research instruments, such as questionnaires or interview prompts.
• To present detailed calculations that would interrupt the main discussion.
• To share supporting tables or additional data.
• To document technical procedures.
• To provide relevant supporting material that readers may want to consult.

However, an appendix shouldn’t become a dumping ground for unrelated information. Each section should serve a clear purpose and support the document.

How to Label Multiple Appendices

When a document contains several appendices, writers often label them with letters or numbers.

A letter-based system might look like this:

Label	Example content
Appendix A	Survey Questionnaire
Appendix B	Supplementary Data
Appendix C	Interview Guide

In the main text, you could write, “The complete questionnaire appears in Appendix A.”

If you refer to all three sections together, you could write, “The appendices provide the supporting materials.”

Some publishers use different numbering systems or heading formats. Follow the relevant guidelines rather than assuming every document uses the same convention.

Where Do Appendices Belong in a Paper?

Appendices generally appear toward the end of a document, after the main discussion. Their exact placement can vary.

For example, a university may require appendices to follow the reference list, while another publication may specify a different order. Some books also place an appendix at the end of an individual chapter when readers need that material immediately.

The Chicago Manual of Style explains that appendixes usually follow the final book chapter, while an appendix may appear at the end of a chapter when its contents are essential to understanding that chapter.

The Chicago Manual of Style Online

The practical rule is straightforward: put supplementary material where your readers can find it easily and follow your required formatting guidelines.

Common Mistakes When Using Appendices and Appendixes

Even experienced writers sometimes hesitate over these spellings. Most mistakes come from assuming that English has only one acceptable plural form or overlooking the context.

Assuming Appendixes Is Always Wrong

This is one of the most common misconceptions.

Appendixes is an accepted plural form of appendix. It follows the regular English pattern of adding -es to the singular noun.

For example, “The book contains two appendixes” is grammatically acceptable. You can use appendices instead if it suits your style guide or audience better.

Assuming Appendices Must Always Refer to Documents

Although appendices is familiar in academic writing, the word’s use isn’t limited to one type of publication. More importantly, dictionaries distinguish between the usual plural forms for different meanings.

For anatomical structures, appendixes is the standard preference in major learner’s dictionaries. For supplementary sections in books and reports, both forms are accepted, with appendices often preferred.

Oxford Learner’s Dictionaries

Mixing Both Forms Without a Reason

Using both spellings in one document can distract readers, particularly when the same meaning appears throughout.

Imagine a report that refers to its supplementary sections as appendices in one chapter and appendixes in another. Although both forms are valid, readers might wonder whether the writer intended a distinction.

Choose one form for document-related usage and apply it consistently. If your subject requires different terminology, make sure the distinction is intentional.

Confusing Singular and Plural Forms

Remember the basic pattern:

Number	Correct form	Example
Singular	Appendix	The appendix contains one table.
Plural	Appendices	The appendices contain three tables.
Plural	Appendixes	The appendixes contain three tables.

The plural forms take plural verbs when they function as the subject of a sentence.

For example, write “The appendices contain the results,” not “The appendices contains the results.”

Ignoring Institutional Requirements

A spelling can be correct in general English but still differ from a publication’s preferred style. This is why academic writers should check their instructions before submitting work.

If your university template uses Appendices, follow it. If your publisher specifies Appendixes, use that form instead. Consistency with the required style is more useful than changing a document to match a personal preference.

Appendices vs. Appendixes: Frequently Asked Questions

Is Appendices or Appendixes Correct?

Both appendices and appendixes are correct plural forms of appendix. For supplementary sections in a book or report, either spelling is acceptable. Appendices is a familiar choice in academic writing, while appendixes is the usual plural for the anatomical meaning.

Is Appendices More Formal Than Appendixes?

Appendices is commonly associated with academic papers, dissertations, and formal reports. However, appendixes is also grammatically correct and can appear in professional writing. The best choice depends on the style guide, publication, and intended meaning.

What Is the Plural of Appendix in American English?

In American English, both appendices and appendixes are accepted for supplementary sections in books and documents. When referring to the body part, appendixes is the usual plural form.

Is Appendixes the Correct Plural for the Body Part?

Yes. Appendixes is the usual plural when discussing multiple anatomical structures. For example, “The medical researchers examined the appendixes of the specimens.” In ordinary medical writing, however, people usually discuss one person’s appendix rather than multiple appendixes.

Should a Research Paper Use Appendices or Appendixes?

Appendices is a sensible default for a research paper when no specific instructions apply. It is familiar in academic writing and clearly identifies supplementary sections. However, if your university, journal, or publisher requires appendixes, follow that guidance.

Can I Use Appendices and Appendixes in the Same Document?

You can use both forms because neither is inherently incorrect. However, when they refer to supplementary sections, choosing one form throughout the document generally makes your writing more consistent. Different contexts or an explicit editorial requirement may justify using different forms.

Why Does Appendix Have Two Plural Forms?

English retains some traditional plural forms from Latin while also allowing regular English endings. Appendices follows the traditional Latin-derived pattern, while appendixes follows regular English pluralization. Both forms have become established in modern usage.

Is Appendixs a Correct Spelling?

No. Appendixs is not a standard plural spelling. Use appendices or appendixes when referring to more than one appendix.

Conclusion

Both appendices and appendixes are correct plural forms of appendix. The main difference is how writers typically use them. Appendices is a familiar choice for supplementary sections in research papers, books, and formal reports, while appendixes is the usual plural when referring to anatomical structures. Both forms are accepted for document-related material.

When writing an academic paper, start with appendices unless your style guide says otherwise. For other types of writing, choose the form that fits your context and keep it consistent. Once you understand the difference, there’s no need to second-guess every occurrence. Follow the relevant guidelines, use the correct grammatical agreement, and let your writing do its job.