Appendices and appendixes are both correct plural forms of appendix. For extra sections at the end of a report, book, thesis, or research paper, appendices is the safest and most familiar choice, especially in academic writing. Appendixes is also grammatically correct and is often used for the body organ. The important rule is to choose the form that fits your context and use it consistently.
What Is the Difference Between Appendices and Appendixes?
Appendices and appendixes are two plural forms of the singular noun appendix.
The basic pattern is:
- One: appendix
- More than one: appendices or appendixes
The two forms can refer to multiple sections added to a document:
The report contains three appendices.
You could also write:
The report contains three appendixes.
The second sentence is grammatically possible because appendixes is an established English plural, not a spelling mistake. Dictionaries recognize both forms.
The difference becomes more useful when you consider context.
For supplementary material in a book, report, or academic paper, appendices is especially familiar:
See Appendices A and B for the complete survey results.
When referring to the anatomical organ, appendixes is commonly used:
The surgeons examined the patients’ appendixes.
This distinction is a strong practical guide, but it should not be treated as an absolute grammatical rule. Both plural forms exist in English.
Why It Matters
Choosing the right plural form may seem like a tiny detail, but small word choices can affect how polished a document looks.
Imagine submitting a 100-page research paper and using Appendix A, Appendix B, and Appendixes C and D without any reason for changing the spelling. The grammar may not be fundamentally wrong, but the inconsistency can make the document look poorly edited.
This matters particularly in:
- Academic papers
- University assignments
- Theses and dissertations
- Business reports
- Research documents
- Books
- Technical manuals
- Legal documents
- Professional reports
In academic writing, appendices is a particularly familiar choice. For example, APA materials use appendices as the plural form.
So, if you are unsure and are talking about supplementary sections in a formal document, appendices is usually the easiest choice.
Read More: Sence vs Sense: Which Spelling Is Correct?
The Core Rule
Appendix = one
Appendices = more than one
Appendixes = more than one
Both appendices and appendixes are correct plurals.
For a report, thesis, book, or academic paper, appendices is generally the more familiar choice.
For the anatomical meaning, appendixes is commonly used.
Oxford notes that appendixes is usually used for the body-part sense, while appendices is usually used for the document sense.
The simplest rule to remember
If you are talking about extra sections at the end of a document, choose:
appendices
If you are talking about multiple anatomical appendixes, choose:
appendixes
But remember: this is a usage preference, not a rule saying that one form is always grammatically correct and the other is always wrong.
How to Use Appendices
Use appendices when a document contains more than one supplementary section.
An appendix normally contains information that supports the main text but is too detailed, lengthy, or specialized to place in the main body.
For example:
The complete interview transcripts are included in the appendices.
The statistical tables appear in Appendices A and B.
Please refer to the appendices for the full questionnaire.
In academic writing, appendices may contain material such as:
- Survey questionnaires
- Interview transcripts
- Large data tables
- Detailed calculations
- Research instruments
- Supporting documents
- Extended methodology
- Additional figures
- Technical information
APA guidance, for example, uses separate labels such as Appendix A, Appendix B, and so on when a paper contains multiple appendices.
When to use appendixes
Appendixes is also a legitimate plural.
It can be used when referring to multiple anatomical appendixes:
The patients had their appendixes removed.
It can also refer to multiple supplementary sections:
The book contains several detailed appendixes.
So you should not assume that appendixes is incorrect simply because appendices sounds more formal.
When to use appendices
For most formal documents, appendices is the safer default:
The report includes three appendices.
The appendices contain the raw survey data.
See Appendices A through C.
This is especially useful when your institution, publisher, editor, or style guide expects that form.
Correct Examples
Here are examples showing how appendices and appendixes work in different situations.
- Conversation:
“The report has two appendices with additional information.” - Email:
“I’ve attached the revised appendices to this email.” - School:
“The teacher asked us to review the appendices before the exam.” - University:
“The interview transcripts are included in the appendices.” - Workplace:
“The financial calculations are provided in Appendix B.” - Academic writing:
“The study’s questionnaires are reproduced in the appendices.” - Business report:
“Please see Appendices A and B for supporting figures.” - Book:
“The author included several appendices containing historical records.” - Medical context:
“The surgeons operated on several patients with inflamed appendixes.” - General writing:
“The document contains four appendixes with supporting material.”
The key point is that both plural spellings can function grammatically. Context helps determine which one sounds most natural.
Incorrect vs. Correct
The biggest mistakes are usually not about choosing appendices instead of appendixes. They involve treating one as wrong, using the singular when a plural is needed, or changing forms unnecessarily.
| ❌ Incorrect | ✅ Correct | Why |
|---|---|---|
| The report contains three appendix. | The report contains three appendices. | Three requires a plural noun. |
| See Appendix A and B. | See Appendices A and B. | Two separate sections require the plural. |
| The report has two appendiceses. | The report has two appendices. | Appendiceses is not a standard plural. |
| The paper includes several appendixes. | The paper includes several appendixes. | This is grammatically acceptable. |
| The patients had their appendices removed. | The patients had their appendixes removed. | Appendixes is the usual plural for the anatomical sense. |
| The thesis contains five appendixes. | The thesis contains five appendices. | Appendixes is possible, but appendices is the more familiar academic choice. |
| The appendices A and B contains data. | The appendices A and B contain data. | The plural subject takes the plural verb contain. |
| The appendix contain the results. | The appendix contains the results. | A singular subject takes contains. |
| Please read the appendiceses. | Please read the appendices. | The plural is appendices, not appendiceses. |
| I added two appendix to the report. | I added two appendices to the report. | A number greater than one requires a plural. |
| The appendixes was useful. | The appendixes were useful. | A plural subject requires the plural verb were. |
| See Appendix A and Appendix B in the appendices. | See Appendices A and B. | The shorter form is clearer when referring to multiple sections. |
Why People Make This Mistake
The confusion exists because appendix comes from Latin, while English also has a very productive way of forming plurals.
The traditional plural is:
appendix → appendices
English also allows:
appendix → appendixes
That creates two legitimate forms.
Latin influence
Appendices follows a traditional plural pattern associated with the word’s Latin origin.
The spelling may look unusual if you are thinking only in terms of ordinary English plurals.
Regular English plural formation
English often adds -es to words ending in -x:
- box → boxes
- fox → foxes
- tax → taxes
So appendix → appendixes follows a pattern that feels natural in English.
Pronunciation adds to the confusion
The two forms are not pronounced the same way.
Appendices is commonly pronounced approximately:
uh-PEN-dih-seez
Appendixes is commonly pronounced approximately:
uh-PEN-dik-siz
This means that hearing one form does not necessarily tell you which spelling the speaker would choose.
Translation interference
Learners may also expect English to preserve the plural system of another language.
That can make appendices seem like the only possible form because it looks more “classical,” or make appendixes seem more logical because it follows a familiar English pattern.
Neither assumption is necessary.
Common Mistakes Checklist
Mistake 1: Thinking appendixes is always wrong
It isn’t.
Appendixes is a recognized plural form of appendix.
How to avoid it:
Remember that both forms are valid.
Mistake 2: Assuming appendices is always required
It isn’t.
You can correctly use appendixes in contexts where that form is appropriate.
How to avoid it:
Choose based on context and any required style guide.
Mistake 3: Using appendix after a plural number
Incorrect:
The report contains three appendix.
Correct:
The report contains three appendices.
How to avoid it:
After two, three, several, many, or another plural quantity, use a plural noun.
Mistake 4: Writing appendiceses
Incorrect:
The document contains several appendiceses.
Correct:
The document contains several appendices.
There is no need to add another plural ending.
Mistake 5: Switching forms randomly
A document can contain both words in English, but switching between them without a reason can look inconsistent.
How to avoid it:
Choose one form for the same document context and stay with it.
Mistake 6: Confusing appendix with annex
An appendix and an annex can both contain additional information, but they are not automatically interchangeable. Their meanings and uses can vary by field and document type.
How to avoid it:
Use the terminology required by your document, institution, industry, or legal framework.
Read More: Summarize vs Summarise: Which Spelling Is Correct?
Appendices vs Appendixes in Real English
When talking about a report or academic paper
In real-world formal writing, appendices is a very natural choice for multiple supplementary sections.
The methodology is explained in detail in the appendices.
This form is especially familiar in academic contexts, where writers routinely refer to Appendix A, Appendix B, and multiple appendices. Academic guidance commonly uses this form.
When talking about the human body
Appendixes is particularly natural when the meaning is anatomical.
The surgeons removed two inflamed appendixes.
Major dictionaries recognize this usage. Oxford specifically notes that appendixes is usually used for the body-part sense.
When both forms are grammatically possible
For document-related writing, appendixes is not automatically unnatural.
For example:
The book contains several appendixes.
A reader will understand it immediately, and the plural is grammatically established.
However, appendices may feel more expected in academic or formal document writing.
So the practical distinction is:
- Grammatically correct: appendices and appendixes
- Especially familiar for document sections: appendices
- Especially common for the anatomical meaning: appendixes
- Best practice: follow the required style and remain consistent
American vs. British English
There is a genuine usage difference worth knowing, but it should not be exaggerated into a rule that completely separates American and British English.
Dictionaries show that both plural forms exist in English. Oxford gives appendixes and appendices, noting that appendixes is usually used for the anatomical sense and appendices for the document sense.
Collins similarly identifies appendices as a common British form for the document meaning, while American English recognizes both appendixes and appendices.
For an international audience, therefore, it is safest not to say:
“Appendices is British and appendixes is American.”
That is too simple.
A better explanation is:
Both forms belong to standard English, but their frequency and preferred contexts vary by dialect, meaning, and style.
Formal vs. Informal Usage
The difference between appendices and appendixes is not simply a formal-versus-informal distinction.
You should not assume that:
appendices = formal
appendixes = informal
That rule is too broad.
Appendices is particularly common in formal and academic documents, so it is a very safe choice in a thesis, research paper, or professional report.
Appendixes is also standard English. It can appear in professional and formal writing, especially when referring to anatomical structures.
If a publisher, university, employer, or style guide specifies one form, follow that instruction.
Read More: Cancellation vs Cancelation: Which Spelling Is Correct?
Comparison Table
| Feature | Appendices | Appendixes |
|---|---|---|
| Singular | Appendix | Appendix |
| Number | Plural | Plural |
| Meaning | More than one appendix | More than one appendix |
| Grammar | Correct | Correct |
| Document sections | Very common | Also possible |
| Academic writing | Very common | Acceptable depending on style |
| Anatomical meaning | Possible | Particularly common |
| Pronunciation | Usually “-seez” | Usually “-siz” |
| Origin/pattern | Traditional plural | Regular English plural |
| Best approach | Use when appropriate | Use when appropriate |
| Consistency | Important | Important |
Appendices vs Appendixes: Which One Should You Use?
If your question is simply “Which should I use?”, the answer depends on what you are writing.
For a thesis or research paper
Use appendices unless your required style guide says otherwise.
The raw data are included in the appendices.
For a business report
Appendices is a strong default.
See Appendices A and B for detailed financial information.
For a book
Appendices is also a familiar choice.
The appendices provide additional historical information.
For medical or anatomical writing
Appendixes is especially natural.
The study examined patients who had undergone surgery on their appendixes.
If your style guide gives a specific instruction
Follow the style guide.
This is more important than trying to apply a universal rule about which spelling is “better.”
For example, academic style systems can specify their own preferred terminology. APA materials use appendices as the plural.
Read More: Spicey vs Spicy: Correct Spelling & Usage.
Memory Trick
Use this simple memory trick:
Documents have appendICES. Bodies have appendIXES.
Think:
Appendices → extra pieces in academic documents
Appendixes → body parts
This is not a rule that makes the alternative form grammatically wrong. It is simply a practical way to remember the most familiar choice for each context.
If you are writing a thesis, report, or book, think:
“Extra information? Appendices.”
Real-Life Situations
Interview
Situation: You are interviewing for a research position.
You say:
“The complete survey methodology is included in the appendices.”
That sounds natural because you are referring to supporting sections in a research document.
Meeting
Situation: You are presenting a business report.
You say:
“The detailed calculations are in Appendix B.”
Because there is only one section being referenced, the singular appendix is appropriate.
Situation: You are sending a report to your manager.
You write:
“I’ve attached the report and included the supporting documents in the appendices.”
Text message
Situation: A classmate asks where the detailed tables are.
You reply:
“Check the appendices at the end of the paper.”
Medical conversation
Situation: A doctor is discussing several patients.
You might hear:
“Two patients had complications involving their appendixes.”
Here, appendixes is natural because the word refers to anatomical organs.
Exam
Situation: A student is asked to identify the plural of appendix.
The strongest answer is:
Appendices or appendixes
If the question is specifically about academic documents, appendices is the expected choice in many contexts.
Expert Tips
1. Don’t call appendixes a spelling mistake
If someone writes appendixes, do not automatically correct it to appendices. First ask what the word refers to.
2. Context is more useful than memorization
Instead of memorizing “one is right and one is wrong,” remember that English has two accepted plurals.
3. Consistency matters
If your report uses appendices, keep using appendices throughout unless there is a genuine reason to change.
4. Follow the house style
A university, publisher, journal, employer, or organization may have its own preferred style.
5. Don’t confuse singular and plural
Use:
Appendix A
but:
Appendices A and B
6. Check the meaning before choosing
If you mean supplementary sections in a paper, appendices is usually the natural formal choice.
If you mean multiple anatomical organs, appendixes is particularly common.
7. Don’t overthink the Latin
Knowing that appendices comes from a traditional Latin plural pattern can help explain the spelling, but you don’t need Latin knowledge to use the word correctly.
FAQ
Is appendices the plural of appendix?
Yes. Appendices is a correct plural of appendix. Appendixes is also a correct plural.
Is appendixes grammatically correct?
Yes. Appendixes is an established plural form of appendix, not a spelling error.
Which is better: appendices or appendixes?
For supplementary sections in academic or formal documents, appendices is generally the safer and more familiar choice. Appendixes is also correct.
Is appendices more formal than appendixes?
Appendices is strongly associated with formal and academic document writing, but appendixes is not inherently informal or incorrect.
Should I write appendices in a research paper?
Yes, appendices is a standard choice for multiple supplementary sections in academic writing. APA materials, for example, use appendices.
Is appendixes used for body parts?
Yes. Appendixes is particularly common for the anatomical meaning of appendix.
Can I use appendixes for a book?
Yes. Appendixes is grammatically possible for multiple supplementary sections in a book. However, appendices is a very familiar choice in this context.
Can I use both appendices and appendixes in one document?
Technically, both are valid forms, but randomly switching between them is best avoided. Choose the form that fits your style and use it consistently.
What is the plural of Appendix A?
If you are referring to several labeled sections, write Appendices A, B, and C.
Is appendices a Latin plural?
The form appendices reflects the traditional plural pattern inherited from the Latin form of the word. English also developed the regular plural appendixes.
How do you pronounce appendices?
Appendices is commonly pronounced approximately uh-PEN-dih-seez.
How do you pronounce appendixes?
Appendixes is commonly pronounced approximately uh-PEN-dik-siz.
Mini Quiz
| # | Question | Answer | Explanation |
|---|---|---|---|
| 1 | What is the plural of appendix? A) Appendixs B) Appendices C) Appendiceses | B) Appendices | Appendices is a correct plural. Appendixes is also accepted. |
| 2 | Complete the sentence: “The report contains three ___.” | appendices | A formal report commonly uses appendices for supplementary sections. |
| 3 | Is “appendixes” correct? | Yes | Appendixes is an established plural form. |
| 4 | Correct the sentence: “See Appendix A and B.” | See Appendices A and B. | Two sections require the plural appendices. |
| 5 | Which is especially common for the anatomical meaning? A) Appendices B) Appendixes | B) Appendixes | Appendixes is particularly common when referring to body organs. |
| 6 | Complete: “The interview transcripts are included in the ___.” | appendices | Appendices is a familiar choice for supplementary academic material. |
| 7 | Correct this sentence: “The appendices was useful.” | The appendices were useful. | Appendices is plural, so it takes were. |
| 8 | Which is correct? A) Two appendix B) Two appendices C) Two appendixs | B) Two appendices | A plural quantity requires a plural noun. |
| 9 | Is “appendiceses” a standard plural? | No | The accepted forms are appendices and appendixes. |
| 10 | Which is the safest choice for a formal research paper? A) Appendices B) Appendixes | A) Appendices | Appendices is especially familiar in academic writing and is used in APA materials. |
Quick Summary
Appendices and appendixes are both correct plural forms of appendix. For extra sections at the end of a report, book, thesis, or research paper, appendices is usually the safest and most familiar choice. Appendixes is also grammatically correct and is especially common when referring to the anatomical organs. The two forms come from different plural patterns: appendices reflects the traditional Latin-derived form, while appendixes follows a regular English plural pattern. If you are writing for a university, publisher, journal, or organization, follow its preferred style. Otherwise, use appendices for formal document sections and appendixes when the anatomical meaning makes that form natural. Most importantly, choose consistently.
