Appendix or Appendices: Simple Rules for Correct Usage 

If you’re writing a report, research paper, thesis, book, or presentation, you may wonder whether you should use appendix or appendices. Both are correct English words, but they don’t mean exactly the same thing. The main difference is simple: appendix is singular, while appendices is the plural form.

Use appendix when you are referring to one supplementary section or item. Use appendices when you are referring to two or more. For example, you might write, “See Appendix A for the survey questions” but “See Appendices A or B for the supporting data.”

The confusion often comes from the unusual plural form. Unlike many English nouns that simply take -s or -es, appendix traditionally changes to appendices. However, appendixes is also an accepted plural form, particularly in general English. In academic, scientific, and formal writing, appendices is very common.

Appendix or Appendices: Which Is Correct?

Both “appendix” or “appendices” are correct. The choice depends on whether you’re talking about one supplementary section or more than one.

In formal academic and professional writing, appendices is often the preferred plural because it follows the traditional Latin-derived plural pattern.

When to Use “Appendix”

Use appendix when you mean one additional section, document, dataset, chart, table, or collection of supporting material.

For example:

• Please see Appendix A for the full questionnaire.
• The results are provided in the appendix.
• I included an appendix at the end of the report.
• The financial calculations appear in Appendix B.
• Refer to the appendix for additional information.

The word can also have a biological meaning. In anatomy, an appendix is a small tube-like structure attached to the beginning of the large intestine.

When to Use “Appendices”

Use appendices when there is more than one supplementary section.

For example:

• The report contains three appendices.
• See Appendices A, B, and C for the supporting documents.
• The research paper includes several appendices.
• Additional charts are included in the appendices.
• The appendices contain the complete survey results.

A useful shortcut is:

One = appendix
More than one = appendices

What Is the Plural of Appendix?

The traditional plural of appendix is appendices.

For example:

• One appendix
• Two appendices
• Several appendices

Appendixes is also used as a plural in English and is considered acceptable, especially when referring to general documents or supplementary sections. However, appendices is particularly common in academic, scientific, legal, and formal writing.

So, if you’re writing a thesis, dissertation, research paper, or formal report, appendices is usually the safest and most conventional choice for the plural.

Why Is It “Appendices” Instead of “Appendixs”?

The plural appendices comes from the word’s Latin origin. Appendix entered English from Latin, where the plural form was appendices.

English has retained this traditional plural in many formal contexts.

This is similar to other Latin-derived words:

• Index → indexes or indices
• Matrix → matrices
• Vertex → vertices
• Appendix → appendices

That doesn’t mean English always follows Latin plural rules. English often develops alternative plurals over time, which is why appendixes is also found in modern usage.

For most formal writing, however, appendices is a familiar and well-established choice.

Appendix or Appendices in a Report

When writing a report, choose appendix or appendices according to the number of supplementary sections you have.

If your report has one supplementary section, you can write:

Appendix
Survey Questionnaire

If your report has several supplementary sections, you might write:

Appendices
Appendix A: Survey Questionnaire
Appendix B: Interview Questions
Appendix C: Statistical Tables

You can also refer to an individual appendix within a report:

The complete questionnaire is provided in Appendix A.

When referring to more than one:

The supporting documents are provided in Appendices A or B.

Should It Be “Appendix” or “Appendices” in a Report?

Use appendix if the report has one supplementary section and appendices if it has multiple supplementary sections.

For example:

One:

The additional calculations are provided in the appendix.

Multiple:

The additional calculations and survey results are provided in the appendices.

If you label individual sections, use Appendix A, Appendix B, Appendix C, and so on.

Appendix or Appendices in a Table of Contents

The correct choice in a table of contents depends on whether the document contains one or multiple supplementary sections.

For a single section:

For multiple sections:

You can also list individual appendices:

Appendix A: Questionnaire
Appendix B: Raw Data
Appendix C: Additional Figures

This makes it clear to readers exactly where each supporting section is located.

Appendix or Appendices in a Research Paper

In research writing, an appendix contains additional material that supports the main paper but isn’t essential to understanding the main argument.

Examples include:

• Survey questions
• Interview transcripts
• Detailed calculations
• Additional tables
• Raw or supplementary data
• Research instruments
• Extra charts
• Supporting documents

If there is only one such section, call it an appendix.

If there are several, call them appendices.

For example:

The full survey instrument is included in Appendix A.

Or:

The survey instrument and supplementary statistical tables are included in Appendices A or B.

Appendix or Appendices in English

In English, appendix is singular and appendices is a plural form.

The basic grammar is:

Appendix = one

The appendix contains additional information.

Appendices = more than one

The appendices contain additional information.

You may also encounter appendixes as the plural. It is not simply a spelling mistake. It is an accepted English plural, although appendices is especially common in formal and academic contexts.

How Do You Pronounce Appendix?

Appendix is commonly pronounced:

uh-PEN-diks

IPA:

/əˈpɛndɪks/

It has three syllables:

a · pen · dix

The main stress falls on the second syllable:

a-PEN-dix

For example:

The report includes an appendix.

Don’t pronounce the final -ix as though it were a separate long vowel sound. The ending sounds roughly like “diks.”

How Do You Pronounce Appendices?

Appendices is commonly pronounced approximately:

uh-PEN-di-seez

IPA:

/əˈpɛndɪsiːz/

It has four syllables:

a · pen · di · ces

The main stress remains on the second syllable:

a-PEN-di-seez

For example:

The report contains several appendices.

The pronunciation changes noticeably from the singular because the plural ending -ices is pronounced like -ee-seez.

Appendix vs. Appendices: Quick Comparison

The most important distinction is number, not meaning.

Can “Appendixes” Also Be Correct?

Yes. Appendixes is an accepted plural of appendix.

You may therefore see both:

• appendices
• appendixes

However, they aren’t equally common in every context. Appendices is strongly established in academic, scientific, technical, and formal writing.

For example, in a research paper, you would commonly see:

The results are presented in Appendices A or B.

In ordinary English, appendixes can also be grammatically acceptable:

The book contains several appendixes.

If you’re unsure which plural to choose for a formal document, appendices is generally the more conventional option.

Appendix or Appendices in PowerPoint

The same singular-versus-plural rule applies to PowerPoint presentations.

If you have one supplementary slide or section, you can label it:

Appendix

If you have several supplementary slides or sections, use:

Appendices

For example, a business presentation might include:

• Appendix A: Financial Data
• Appendix B: Market Research
• Appendix C: Additional Charts

You can also use Appendix as a section heading even if the section contains several related slides, depending on how your presentation is organized. What matters is the structure and whether you’re treating the material as one appendix or several distinct appendices.

When Should You Use an Appendix?

An appendix is useful when you have supporting information that is relevant but would interrupt the flow of the main document.

For example, a report might discuss the results of a survey without placing every survey question in the main text. Instead, the complete questionnaire can go into an appendix.

Good candidates for an appendix include:

• Long questionnaires
• Detailed calculations
• Supplementary tables
• Technical information
• Additional figures
• Interview questions
• Supporting documentation
• Extended data

The main text should remain understandable without forcing the reader to study every appendix.

How to Refer to an Appendix Correctly

When referring to a specific appendix, capitalize Appendix when it is used as part of a formal label.

For example:

See Appendix A for the complete list of questions.

Additional results are presented in Appendix B.

When using the word generally rather than as a specific title, lowercase is usually appropriate:

The additional information is included in the appendix.

For multiple sections:

The supporting data are provided in Appendices A or B.

This distinction makes formal documents easier to navigate.

Common Mistakes With Appendix or Appendices

Mistake 1: Using “Appendix” for Several Separate Sections

Incorrect:

See Appendix A or Appendix B for the additional data.

This sentence isn’t necessarily grammatically wrong because each named section is individually an appendix. However, if you’re referring to both sections collectively, appendices is more natural.

Better:

See Appendices A or B for the additional data.

Mistake 2: Using “Appendices” for One Section

Incorrect:

Please see the appendices for the questionnaire.

If there is only one supplementary section, appendix is more precise.

Correct:

Please see the appendix for the questionnaire.

Mistake 3: Writing “Ppendix”

Incorrect:

The data are included in the ppendix.

Correct:

The data are included in the appendix.

The spelling ppendix is simply a misspelling of appendix. The word begins with ap-, not pp-.

Mistake 4: Assuming “Appendices” Is the Only Plural

It’s common to learn that the plural is appendices, but appendixes is also an accepted plural form.

For formal academic writing, appendices is usually the more conventional choice.

Appendix or Appendices: Which One Should You Use?

The easiest way to choose is to ask yourself one question:

How many supplementary sections am I referring to?

If the answer is one, use appendix.

The report includes an appendix.

If the answer is two or more, use appendices.

The report includes three appendices.

If you’re referring to individual sections, use their labels:

Appendix A
Appendix B
Appendix C

When referring to those sections collectively:

Appendices A, B, and C

This rule works for reports, research papers, theses, dissertations, books, presentations, and other formal documents.

Frequently Asked Questions

Is it appendix or appendices?

Both are correct. Appendix is singular, while appendices is the traditional plural. Use appendix for one supplementary section and appendices for two or more.

Should I say appendix or appendices?

Say appendix when you’re talking about one section and appendices when you’re talking about multiple sections. For example, “See Appendix A” refers to one, while “See Appendices A or B” refers to two.

Do you write appendix or appendices in a report?

Use appendix if your report has one supplementary section and appendices if it has several. You can label multiple sections as Appendix A, Appendix B, and Appendix C.

What is the plural of appendix?

The traditional plural is appendices. Appendixes is also an accepted plural form, but appendices is especially common in academic and formal writing.

Is “appendixes” grammatically correct?

Yes. Appendixes is an accepted English plural of appendix. However, appendices is generally more familiar and conventional in academic, scientific, and formal contexts.

How do you pronounce appendices?

Appendices is commonly pronounced approximately uh-PEN-di-seez, with the main stress on the second syllable. Its IPA pronunciation is /əˈpɛndɪsiːz/.

Is appendix singular or plural?

Appendix is singular. Its traditional plural is appendices. For example, “one appendix” and “two appendices.”

Is “appendix” used in English?

Yes. Appendix is a standard English word. It can refer to supplementary material at the end of a document or, in anatomy, to the small organ attached to the large intestine.

Should I use “appendices” in a research paper?

If your research paper contains multiple supplementary sections, appendices is an appropriate and conventional term. If it contains only one, use appendix.

Is it appendix or appendices in a table of contents?

Use Appendix when there is one supplementary section and Appendices when there are multiple sections. Individual sections can be listed as Appendix A, Appendix B, and so on.

Conclusion

Appendix or appendices is mainly a question of singular versus plural. Appendix refers to one supplementary section or item, while appendices refers to two or more.

For example:

One: See Appendix A for the questionnaire.
More than one: See Appendices A or B for the supporting documents.

The plural appendices is especially common in academic, research, scientific, and formal writing. Appendixes is also an accepted plural, so it isn’t automatically incorrect.

Once you remember one appendix, two or more appendices, the choice becomes straightforward. Use the form that matches the number of supplementary sections you’re referring to, and you’ll have the correct word for reports, research papers, presentations, and other formal documents.

Julian Mercer

I’m Julian Mercer, an English language writer dedicated to helping people master grammar through practical examples and clear explanations. I enjoy teaching grammar in a way that is both engaging and easy to remember.

My work focuses on grammar rules, punctuation, word usage, and writing techniques that readers can apply in everyday life. I believe learning English should be simple, enjoyable, and useful.

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English Grammar in Practice
Writing with Precision