If you are unsure whether the plural of appendix is appendixes or appendices, both forms are correct. The choice often depends on the meaning and context.
Appendices is especially common when referring to supplementary sections at the end of books, reports, research papers, and other documents.
Appendixes is also used for this meaning and is commonly used for the anatomical sense of appendix. Oxford lists both plural forms and notes this difference in usual usage.
So, appendixes is not wrong, and appendices is not the only correct plural. The key is knowing when each form sounds most natural and using your chosen form consistently.
Appendixes or Appendices: Which Is Correct?
Both appendixes and appendices are accepted plural forms of appendix.
| Singular | Plural |
|---|---|
| appendix | appendixes |
| appendix | appendices |
For example:
- The report contains three appendices.
- The book includes several useful appendixes.
- The doctor examined his appendix.
- The medical text describes different appendixes.
The difference becomes clearer when we separate the two main meanings of appendix.
For a body part: appendixes is the usual plural form.
For a section at the end of a book or document: appendices is especially common, although appendixes is also accepted. Oxford specifically identifies this distinction in its usage notes.
Quick Answer
If you are writing an academic paper, thesis, dissertation, or formal report, appendices is a natural and widely used choice.
If you are talking about the body part, appendixes is the usual form.
However, neither plural should automatically be treated as incorrect.
What Does Appendix Mean?
The word appendix has two common meanings.
Appendix as a Section in a Document
In writing, an appendix is a separate section at the end of a book, report, research paper, thesis, or other document. It contains useful supporting information that would make the main text too long or difficult to follow.
For example, a research paper might place the following in an appendix:
- a questionnaire
- interview questions
- detailed calculations
- raw data
- large tables
- additional figures
- research materials
- technical information
The main discussion can then stay focused while readers can consult the appendix when they need more detail.
Academic-writing guidance from Purdue OWL describes appendices as a place for supplementary material that helps readers understand a paper without distracting from its main text.
Example:
The complete survey questions are included in Appendix A.
When there is more than one such section, you can refer to them as appendices.
Appendix as a Body Part
An appendix is also a small, tube-shaped structure attached to the large intestine.
In this sense, appendixes is the usual plural.
Example:
The textbook contains information about the function of the human appendix.
The study compared the anatomy of the appendixes in different animals.
Cambridge lists appendixes as the plural for the body-part meaning, while for the book-part meaning it gives both appendixes and appendices.
What Is the Plural of Appendix?
The plural of appendix can be appendixes or appendices.
This is one of those English nouns that has more than one accepted plural form.
Why Is Appendix Plural Appendices?
Appendices comes from the traditional Latin plural pattern. It has remained common in formal English, particularly when referring to sections of books and academic documents.
You will often see:
See Appendices A and B for the supporting data.
The report contains three appendices.
The appendices provide additional methodological details.
The form is particularly familiar in academic writing. Scribbr, for example, notes that both pluralizations can be used but that appendices is more common, including in APA-style writing.
Why Is Appendixes Also Correct?
Appendixes follows the regular English plural pattern by adding -es.
It is therefore a legitimate English plural rather than a spelling mistake.
For example:
The book contains several detailed appendixes.
The report includes two appendixes with supporting documents.
Cambridge’s dictionary entries also provide examples of appendixes being used for book and document sections.
Appendices vs Appendixes: What’s the Difference?
The main difference is usage and preference, not basic grammatical correctness.
| Appendices | Appendixes | |
|---|---|---|
| Singular | appendix | appendix |
| Number | plural | plural |
| Document sections | Very common | Also correct |
| Academic writing | Very common | Accepted |
| Body-part meaning | Less usual | Usual |
| Pronunciation | uh-PEN-di-seez | uh-PEN-dik-siz |
For most readers, appendices will feel more familiar in a research paper or formal report. However, appendixes is not automatically incorrect in that setting.
This distinction matters because some grammar websites present the two forms as if they were strictly divided into separate meanings. The actual dictionary evidence is more flexible: Cambridge explicitly lists appendixes or appendices for the book-part meaning.
So it is better to think of the distinction as a usual preference, rather than an absolute grammatical rule.
Appendices or Appendixes in a Report
In a report, an appendix contains supporting information that is relevant but does not need to appear in the main discussion.
For example, a business report might include:
- detailed financial tables
- survey results
- technical specifications
- supporting calculations
- lengthy questionnaires
- additional charts
- research data
A report might say:
The complete survey results are provided in Appendix A.
If the report has several supplementary sections:
See Appendices A–C for the detailed results.
Academic and technical-writing guidance generally recommends that appendix material should support the main report rather than become a place for unrelated information. TU Delft, for example, recommends that each appendix have a clear topic and that the main text refer to the appendix when its information is used.
Example of Appendices in a Report
Imagine a market research report about customer satisfaction.
The main report discusses the findings and conclusions. The supporting material could be organized like this:
- Appendix A: Customer Survey
- Appendix B: Detailed Survey Results
- Appendix C: Interview Questions
This structure keeps the main report readable while preserving the evidence behind the findings.
Appendix or Appendices in a Table of Contents?
Use appendix when referring to one section and appendices when referring to multiple sections.
For example:
One section:
Appendix A: Survey Questions
Several sections:
Appendices
A table of contents might look like this:
| Section | Page |
|---|---|
| Introduction | 1 |
| Methodology | 5 |
| Results | 12 |
| References | 20 |
| Appendix A: Survey Questions | 24 |
| Appendix B: Raw Data | 28 |
Universities commonly recommend clearly labeling individual appendices and referring to them in the main text. Oxford Brookes, for example, uses labels such as Appendix 1, Appendix 2, and Appendix 3 and recommends referring to the relevant appendix in the body of the work.
The exact labeling system can vary by institution or style guide, so follow the requirements for your assignment, publisher, or organization.
Appendices in Academic Writing
Appendices are especially common in academic writing because research often produces more supporting material than can comfortably fit into the main discussion.
A thesis might include:
- interview transcripts
- questionnaires
- research instruments
- detailed datasets
- extended tables
- calculations
- coding frameworks
- supplementary figures
For example:
The interview protocol is provided in Appendix A.
Additional statistical results are presented in Appendix B.
Purdue’s academic-writing guidance recommends placing each appendix on its own page and labeling multiple appendices with capital letters, such as Appendix A and Appendix B.
The important point is that an appendix should have a clear purpose. It should not simply be a place to move information that the writer did not know where to put.
How to Label Multiple Appendices
A common system is:
- Appendix A
- Appendix B
- Appendix C
For example:
See Appendix B for the complete interview questions.
A university academic-writing guide similarly recommends giving each appendix a clear title and referring to it from the main report.
How to Pronounce Appendix, Appendices, and Appendixes
The two plural forms have different pronunciations.
Appendix Pronunciation
appendix: /əˈpen.dɪks/
It sounds approximately like:
uh-PEN-diks
Appendices Pronunciation
appendices: /əˈpen.dɪ.siːz/
Approximately:
uh-PEN-di-seez
Cambridge gives this pronunciation for both UK and US English.
Appendixes Pronunciation
appendixes: /əˈpen.dɪk.səz/
Approximately:
uh-PEN-dik-siz
Cambridge lists this pronunciation for appendixes.
The easiest way to remember the difference is:
- appendix → uh-PEN-diks
- appendices → uh-PEN-di-seez
- appendixes → uh-PEN-dik-siz
Appendixes or Appendices Synonym
Appendixes and appendices are not really synonyms in the traditional sense. They are two accepted plural forms of the same noun, appendix.
However, when appendix means a supplementary section, several related words may appear in similar contexts.
These include:
- supplement
- attachment
- annex
- annexure
- supporting material
- supplementary material
- additional section
- exhibit
These terms are not interchangeable in every situation.
For example, a legal document may use annex or exhibit, while an academic paper commonly uses appendix. The correct term depends on the document and its conventions.
Appendixes or Appendices in Sentences
Examples make the difference between these forms easier to understand. The context tells you which plural sounds more natural.
Appendices in a Sentence
- The researchers placed the raw data in the appendices.
- Please see Appendices B and C for the additional tables.
- The thesis contains three appendices.
- The supporting documents are included in the appendices.
Using Appendixes in a Sentence
- The book contains several useful appendixes.
- The report includes two appendixes with supporting documents.
- The medical textbook describes the structure of the appendixes.
- The appendixes provide additional information for readers.
Using Appendix in a Sentence
- See Appendix A for the complete questionnaire.
- The appendix contains the full dataset.
- The researcher added the survey to an appendix.
- The doctor explained the function of the appendix.
Examples With Appendix
Use appendix when you are referring to one section or to the body part.
- See Appendix A for the complete questionnaire.
- The appendix contains the full dataset.
- The researcher added the survey to an appendix.
- The doctor explained the function of the appendix.
These examples show why context matters more than simply labeling one spelling “right” and the other “wrong.”
Common Mistakes With Appendix Plurals
1. Treating Appendixes as Incorrect
Appendixes is a valid plural form. It should not automatically be marked as a spelling error. Cambridge lists it as a plural of appendix.
2. Using Appendix for More Than One Section
If you are talking about multiple sections, use a plural:
The report contains three appendices.
Not:
The report contains three appendix.
3. Assuming Appendices Is Always Required
For document sections, appendices is very common, but appendixes is also accepted. Cambridge explicitly gives both forms for the book-part meaning.
4. Switching Forms Without a Reason
If you choose appendices for a report, keep that form throughout the document unless a specific style requirement says otherwise.
Consistency makes formal writing easier to read.
5. Confusing an Appendix With an Annex
An appendix and an annex can both contain supplementary material, but they are not universal substitutes for one another. The preferred term depends on the type of document, institution, publisher, or professional context.
Appendix vs Annex: Are They the Same?
Not exactly.
An appendix is generally a supplementary section attached to a larger document. An annex can also provide additional information, but the two words have different conventions in different fields.
For example, a research paper may contain an appendix with interview questions. A legal, governmental, or technical document may use an annex for additional material.
The safest approach is to follow the terminology used by the relevant organization, publication, or style guide.
Which Form Should You Use?
The simplest practical rule is:
Use “appendices” for formal documents when you want the most familiar conventional choice.
For example:
The supporting data are included in Appendices A and B.
Use “appendixes” when referring to the body part.
The anatomy text compares the appendixes of several species.
But remember that appendixes can also refer to document sections. It is an accepted plural form, not an error. Oxford and Cambridge both support the broader usage, although Oxford identifies different usual preferences by sense.
If your university, publisher, employer, or style guide specifies one form, follow that requirement. Otherwise, choose a form that suits your context and use it consistently.
FAQs
1. Is appendixes a correct word?
Yes. Appendixes is a correct plural of appendix. It is especially common for the anatomical meaning, but it can also refer to supplementary sections in books and documents.
2. Is appendices the plural of appendix?
Yes. Appendices is an accepted plural of appendix and is particularly common when referring to supplementary sections in books, reports, and academic documents.
3. Are appendixes and appendices both correct?
Yes. Both are accepted plural forms. The preferred form depends on meaning, context, and sometimes the style guide being followed.
4. What is the plural of appendix?
The plural can be appendices or appendixes.
5. Should I use appendices or appendixes in a report?
Appendices is a very common choice for reports, especially in academic writing. However, appendixes is also grammatically acceptable. Follow your institution’s style requirements if one exists.
6. Is appendices more formal than appendixes?
Appendices is often perceived as the more traditional or conventional form in formal and academic writing. However, it is not accurate to say that appendixes is simply informal or incorrect.
7. How do you pronounce appendices?
Appendices is pronounced approximately uh-PEN-di-seez. Cambridge gives /əˈpen.dɪ.siːz/ for both UK and US English.
8. How do you pronounce appendixes?
Appendixes is pronounced approximately uh-PEN-dik-siz, with the pronunciation /əˈpen.dɪk.səz/ listed by Cambridge.
9. What is the difference between an appendix and an annex?
Both can refer to additional material attached to a document, but their use varies by context. An appendix is especially common in academic and general writing, while annex is common in certain legal, governmental, and technical contexts.
10. How do you list multiple appendices in a table of contents?
You can label them individually, such as Appendix A, Appendix B, and Appendix C, depending on your required style. Academic institutions commonly recommend clear labels and references to each appendix in the main text.
Conclusion
Both appendixes and appendices are correct plural forms of appendix. The form you choose depends mainly on context. For supplementary sections in reports, books, theses, and research papers, appendices is especially common.
For the anatomical meaning, appendixes is the usual choice. Still, appendixes can also be used for document sections, so it should not be treated as an error.
If your university, publisher, or style guide has a specific preference, follow it. Otherwise, choose the form that fits your context and use it consistently.
Knowing this distinction makes it easier to write clearly whether you are preparing an academic paper, business report, book, or everyday English sentence.
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