Appendices vs Appendixes can confuse writers because both plural forms of appendix appear in real texts, dictionaries, and formal writing today.
The short answer is that appendices and appendixes are both correct, although appendices was historically the preferred plural in many contexts. Older real texts often favored it in the literary sense and medical sense, while modern English accepts both forms. When I check this kind of grammar issue, I focus on the actual usage and style rather than getting stuck on which spelling looks more right. Understanding the meanings makes it easier to avoid unnecessary confusion or switch between forms.
The pattern becomes clearer when you look at foreign-derived words and their plural endings. English has gradually Anglicized many words that once kept their original forms. English dictionaries show examples such as gymnasiums and gymnasia, memorandums and memoranda, syllabuses and syllabi, and cactuses and cacti. The same development helps explain why appendices and appendixes exist. A dictionary from about 150 years ago would have recommended appendices as the plural of appendix, whereas modern references commonly recognize both. The American Heritage Dictionary of the English Language also records the two plurals, giving writers, students, and professionals a useful reference when choosing the correct usage.
In academic writing, reports, research papers, books, publishing, and formal documentation, consistency is an important part of clear writing. One of the most common errors is using appendices in one section and appendixes in another without a clear reason. A practical guide is to check the style rules of your institution, publisher, or project, then use one form consistently. In real-world applications, this approach can reduce inconsistency and make your work clear, confident, and stress-free to read. The same difference applies when a doctor discusses more than one anatomical appendix; the accepted form depends on style and context, whether the subject involves people, medicine, or documents.
What Does Appendix Mean?
An appendix is an additional section placed at the end of a document, book, report, thesis, dissertation, or similar work. It contains supporting information that matters to the reader but doesn’t need to appear in the main discussion.
Think of an appendix as a detailed toolbox. The main article explains the important points, while the appendix stores useful material that supports those points.
For example, a research paper might discuss the results of a survey in the main text. Instead of filling several pages with every survey question and response, the writer can place the complete questionnaire in an appendix.
Common material found in an appendix includes:
- Raw research data
- Detailed tables
- Survey questionnaires
- Interview questions
- Technical specifications
- Mathematical calculations
- Supporting charts
- Research instruments
- Detailed methodologies
- Supplementary documents
- Additional examples
- Source information
An appendix shouldn’t simply become a dumping ground for unrelated information. The material should support, clarify, document, or expand something discussed in the main document.
The word appendix also has an anatomical meaning. In medicine, it refers to the vermiform appendix, a narrow, finger-shaped pouch connected to the beginning of the large intestine. Context usually makes the intended meaning obvious.
For example:
“The research questionnaire appears in the appendix.”
Here, appendix means a document section.
“The patient underwent surgery to remove the appendix.”
Here, it refers to the anatomical structure.
What Does Appendices Mean?
Appendices is a plural form of appendix. It traditionally comes from the Latin plural pattern associated with the word.
When a document contains two or more supplementary sections, you can call them appendices.
For example:
“The dissertation contains three appendices.”
This means the dissertation has three separate supplementary sections.
You might also see formal labels such as:
- Appendix A — Survey Questionnaire
- Appendix B — Interview Transcript
- Appendix C — Statistical Data
When referring to more than one of these sections in a sentence, appendices works naturally:
“The supporting evidence appears in Appendices A and B.”
The form is especially familiar in academic writing, research papers, dissertations, books, scientific reports, and formal documentation.
It also follows a broader pattern found in English words that entered the language from Latin and Greek. English sometimes preserves a classical plural while also developing a regular English plural. That is exactly what happened with appendix.
What Does Appendixes Mean?
Appendixes is also an accepted plural form of appendix.
Instead of changing the ending according to the traditional Latin pattern, this form creates the plural using the ordinary English -es ending.
For example:
“The manual contains several appendixes covering installation and maintenance.”
The sentence is grammatically sound. Appendixes means more than one appendix.
You’ll sometimes see this form in general English and in publications that favor regular English plurals. It can also appear in professional and technical writing.
The important point is simple: appendixes isn’t a spelling mistake merely because appendices is more familiar in formal writing.
English contains many words with competing plural forms. Some retain an older classical form, while others use a regular English ending. Over time, both forms can become established.
That makes appendixes a legitimate word rather than a careless variation.
Appendices vs Appendixes: What’s the Difference?
The main difference between appendices and appendixes is the way the plural is formed.
Appendices uses the traditional plural associated with the word’s Latin history. Appendixes applies the regular English plural ending.
In ordinary usage, however, both refer to multiple appendices.
| Feature | Appendices | Appendixes |
| Singular | Appendix | Appendix |
| Number | Plural | Plural |
| Basic meaning | More than one appendix | More than one appendix |
| Formation | Traditional/classical | Regular English |
| Common in formal writing | Yes | Yes, though less traditional |
| Grammatically valid | Yes | Yes |
| Suitable for academic writing | Yes | Yes, subject to style requirements |
This distinction matters because writers sometimes assume that only the classical form can be correct.
That’s too strict.
If you write, “The report includes two appendixes,” you’re still communicating the correct plural meaning. If you write, “The report includes two appendices,” you’re also correct.
The real question often becomes which form fits the style of your document.
Is Appendices or Appendixes Correct?
Both appendices and appendixes are correct plural forms of appendix.
Major dictionaries recognize the two forms. For example, Merriam-Webster lists appendixes and appendices as plural forms of appendix.
You can verify the dictionary entry here:
Cambridge Dictionary also provides information about appendix and its plural usage:
That distinction is useful because grammar and style aren’t always the same thing.
A dictionary can recognize multiple forms while a university, publisher, journal, or company style guide prefers one. In that situation, the style requirement determines which form you should use.
For example, if your university’s thesis manual consistently uses appendices, use appendices throughout your thesis. Don’t switch to appendixes simply because another dictionary recognizes it.
Consistency matters more than forcing one form into every situation.
Why Does Appendix Have Two Plural Forms?
The answer lies partly in the history of English.
Appendix entered English through Latin. Traditional Latin-derived vocabulary often preserves older plural patterns. That’s where appendices comes from.
English, however, doesn’t always preserve foreign plural systems indefinitely. Speakers frequently adapt borrowed words to normal English grammar. Adding -es to create appendixes follows a familiar English pattern.
This creates two established forms:
Appendix → appendices
and
Appendix → appendixes
The process isn’t unusual. English has borrowed thousands of words from other languages and has often adapted them to English grammar.
This is one reason English can have multiple accepted forms for a single plural. Language doesn’t always follow one neat mathematical rule. Historical usage, pronunciation, borrowing, and everyday speech all shape the vocabulary.
The key takeaway is that appendices isn’t simply an irregular spelling invented by modern writers. It reflects the word’s classical history, while appendixes reflects English’s tendency to regularize borrowed words.
Appendices vs Appendixes in Academic Writing
Academic writing is where you’ll most frequently encounter appendices.
A thesis might contain several supplementary sections, each containing information that supports the research without interrupting the main argument.
For example:
Appendix A — Survey Questions
Appendix B — Participant Demographics
Appendix C — Statistical Tables
The main text can then refer readers to those sections:
“The complete questionnaire is provided in Appendix A.”
Or:
“Additional statistical results appear in Appendices B and C.”
This structure keeps a long research paper readable. Imagine a 100-page dissertation that inserted every questionnaire, data table, and calculation directly into the main chapters. The argument could become difficult to follow.
Appendices solve that problem by moving supporting details to the back.
When Academic Writers Use Appendices
An appendix can be useful for:
- Research questionnaires
- Interview transcripts
- Detailed statistical results
- Long data tables
- Experimental procedures
- Mathematical derivations
- Coding information
- Additional figures
- Supporting documents
However, not every piece of extra information deserves an appendix.
A useful rule is this: if readers need the information to understand your central argument, it probably belongs in the main text. If they might want to inspect the supporting details but don’t need them to follow the argument, an appendix may be appropriate.
Appendices vs Appendixes in Business and Professional Writing
Business documents use supplementary sections for much the same reason academic papers do: they keep the main document focused.
A project report might summarize its findings in the main sections and place detailed technical information at the end.
For example:
“The equipment specifications are provided in Appendix B.”
A business proposal could include:
- Pricing tables
- Technical specifications
- Project schedules
- Research data
- Detailed assumptions
- Supporting calculations
A policy document might also use appendices to hold forms, procedures, or reference material.
In these settings, appendices often fits naturally with a formal tone. However, appendixes remains a valid plural if that is the preferred form in the organization’s style.
The safest approach is practical: check the document’s required style and stay consistent.
Appendices vs Appendixes in Legal and Technical Documents
Legal and technical documents often contain large amounts of supporting information.
A technical report, for example, could summarize an engineering test in the main body while placing extensive measurements in an appendix.
Similarly, a contract may contain supplementary material, although legal documents frequently use specific terms such as exhibits, schedules, or annexes. Those terms can have distinct meanings depending on the document and jurisdiction.
That distinction matters.
An appendix isn’t automatically interchangeable with an exhibit or schedule. A legal document can assign each component a specific function.
For technical writing, appendices are particularly useful when the supporting information is detailed but still relevant.
A software documentation package, for instance, might put:
- Configuration tables
- API details
- Compatibility information
- Extended examples
- Error codes
into supplementary sections.
The goal remains the same: support the main document without overwhelming the reader.
Appendices vs Appendixes in Medical and Anatomical Contexts
The word appendix also appears in medical writing, where it usually refers to the anatomical structure.
The plural can appear when discussing multiple structures or multiple anatomical appendages, although medical terminology often depends heavily on the specific anatomical context.
For example, medical writing commonly discusses:
“The patient’s appendix showed signs of inflammation.”
That’s singular.
In contrast, when a writer genuinely refers to multiple structures, a plural form may be required.
This meaning should not be confused with the document-related meaning of appendix.
Compare these two sentences:
“The researcher included the patient questionnaire in the appendix.”
“The surgeon examined the patient’s appendix.”
The first concerns a document. The second concerns anatomy.
Context does the heavy lifting.
How to Use Appendices and Appendixes in a Sentence
Seeing both forms in real sentences makes the distinction easier to remember.
Examples With Appendices
“The complete survey appears in Appendix A.”
“The researchers included three appendices with the dissertation.”
“Additional calculations are provided in Appendices B and C.”
“Refer to the appendices for the complete dataset.”
“The technical drawings are included in the final appendices.”
Examples With Appendixes
“The manual contains several appendixes with troubleshooting information.”
“The report’s appendixes provide additional technical details.”
“Readers can find the supporting charts in the appendixes.”
“The author added two appendixes to the revised edition.”
Notice something important: the meaning doesn’t change simply because the spelling changes.
Examples With Appendix
Use appendix when you’re referring to one:
“See Appendix A for the questionnaire.”
“The thesis includes an appendix containing the raw data.”
“The supporting calculations appear in the appendix.”
The basic pattern is straightforward:
One = appendix
More than one = appendices or appendixes
Read This Also: Hustle vs Hussle: Which Spelling Is Correct?
Common Mistakes With Appendices and Appendixes
Several mistakes appear repeatedly when writers work with this word.
Treating Appendixes as Incorrect
This is the biggest misconception.
Appendixes is an established plural form, so it shouldn’t automatically be marked wrong.
Using Appendix for Multiple Sections
If you write:
“See the appendix A and B.”
the number doesn’t match the noun.
Better:
“See Appendices A and B.”
Each individual section is an appendix. Together, they are appendices or appendixes.
Mixing Forms Without a Reason
Suppose a report says:
“Appendices A and B contain the data. The remaining appendixes appear below.”
That sudden switch can look careless.
There’s no grammatical reason that forces you to use only one form, but switching between forms within the same document can distract readers.
Choose one and use it consistently unless a quotation, title, or required terminology calls for another form.
Forgetting Cross-References
If your document contains Appendix B, the main text should refer to it accurately.
For example:
“The full calculation appears in Appendix B.”
That is clearer than vaguely saying:
“The calculation appears at the end.”
Precise cross-references help readers navigate long documents.
Treating Every Supplement as an Appendix
A supporting file isn’t automatically an appendix.
Depending on the document, you might need an attachment, exhibit, annex, or schedule instead.
How to Label Multiple Appendices Correctly
When a document contains multiple appendices, writers commonly label them with letters.
For example:
| Label | Content |
| Appendix A | Survey questionnaire |
| Appendix B | Raw research data |
| Appendix C | Interview questions |
| Appendix D | Statistical calculations |
This system makes cross-referencing easy.
You could write:
“The interview protocol is provided in Appendix C.”
When referring to several sections, use the plural:
“The supporting materials appear in Appendices A–D.”
Some documents instead use numbers:
- Appendix 1
- Appendix 2
- Appendix 3
Neither system should be chosen randomly. Follow the document’s required style.
Capitalization also depends on whether the word forms part of a formal label.
For example:
“See Appendix B for the complete results.”
Here, Appendix is part of the formal name.
But a general reference can use lowercase:
“The supporting information appears in an appendix.”
Appendices vs Appendixes in Different Style Guides
Style guides exist partly because professional writing needs consistency.
A dictionary tells you whether a word or form exists. A style guide can tell you how a particular type of publication wants writers to use it.
That distinction becomes important for appendices vs appendixes.
Before choosing a form for an academic paper, check:
- Your university’s writing manual
- Your department’s thesis guidelines
- Your journal’s author instructions
- Your publisher’s house style
- Your company’s documentation standards
- The relevant professional style guide
If the required style uses appendices, follow it.
If it permits or prefers appendixes, use that form.
Don’t change a document’s spelling simply because one form looks more sophisticated. Consistency and compliance with the required style matter more.
For dictionary verification, useful references include:
These resources can help confirm the word’s definition and plural forms.
Appendices vs Appendixes: US English Usage
In US English, both appendices and appendixes are recognized plural forms.
For formal writing, appendices is a particularly familiar choice. You’ll commonly encounter it in academic papers, dissertations, books, research reports, and professional documentation.
However, familiarity shouldn’t be confused with exclusive correctness.
Appendixes follows a normal English plural pattern and is also established.
If you’re writing for an American university, publisher, or organization, the best choice may depend on its house style. That’s especially important for long documents where headings, table-of-contents entries, and cross-references must remain consistent.
A practical US English rule is:
Use appendices when it matches the expected formal style. Use appendixes when your chosen or required style permits it.
Either way, avoid switching forms randomly.
Appendices vs Appendixes: Pronunciation
The two plural spellings also have different pronunciation patterns.
Appendices is commonly pronounced approximately:
uh-PEN-dih-seez
Its ending sounds like “-seez.”
Appendixes is commonly pronounced approximately:
uh-PEN-dik-siz
Its ending follows the familiar pronunciation of an English -es plural.
That difference can help you recognize the two forms when listening to a lecture, presentation, audiobook, or conversation.
The singular appendix is commonly pronounced:
uh-PEN-diks
The spelling may look complicated, but the pronunciation becomes easier once you separate the word into sounds.
Appendices vs Appendixes vs Annexes
These words can appear in similar documents, but they aren’t automatically interchangeable.
An appendix usually contains supplementary information attached to a larger document.
An annex can also contain additional material, but its usage varies by field and region. In international, legal, governmental, and technical contexts, an annex can have a specific structural role.
| Term | General meaning | Typical context |
| Appendix | Supplementary section attached to a document | Books, reports, academic work |
| Appendices | Plural of appendix | Formal and academic documents |
| Appendixes | Alternative plural of appendix | General and professional writing |
| Annex | Additional section or document attached to a main document | Legal, governmental, international, technical contexts |
| Annexes | Plural of annex | Formal documentation |
Because terminology can vary by field, don’t replace appendix with annex merely to avoid repetition.
Use the term that matches the document’s structure and applicable style.
Appendices vs Appendixes vs Attachments
An attachment usually refers to something supplied with another document or communication.
For example, an email might say:
“Please review the attached spreadsheet.”
That’s an attachment, not necessarily an appendix.
An appendix, by contrast, is usually integrated into the structure of a larger document.
Consider this comparison:
| Term | Example |
| Appendix | Supporting tables at the end of a research paper |
| Attachment | Spreadsheet sent with an email |
| Exhibit | Evidence or supporting item identified in a legal document |
| Schedule | Detailed material attached to or forming part of certain formal documents |
| Annex | Additional section attached to a larger formal document |
These distinctions become especially important in business and legal writing.
When Should You Use Appendices?
An appendix works best when information is useful but too detailed for the main discussion.
Imagine reading a research paper about consumer behavior. The main text explains the findings, methodology, and conclusions. You probably don’t need to read 30 pages of raw survey responses just to understand the findings.
Putting that material in an appendix gives readers access without forcing everyone through the details.
Consider an appendix when the material:
- Supports a claim made in the main text
- Provides evidence for readers who want deeper detail
- Contains lengthy tables
- Documents research methods
- Includes questionnaires or interview protocols
- Provides calculations that would interrupt the main argument
- Helps readers reproduce or inspect the work
However, don’t hide essential information in an appendix.
If a table is necessary for understanding your central argument, placing it 40 pages away may frustrate readers. Put important evidence where readers need it.
A Practical Case Study: Using Appendices in a Research Report
Consider a fictional university research report studying how students use digital learning platforms.
The researchers collect:
- Responses from 1,200 students
- A 25-question survey
- Demographic information
- Detailed statistical calculations
- Interview questions
- Several long data tables
Putting all of this into the main report would make the document cumbersome.
Instead, the researchers could structure the report like this:
Appendix A — Survey Questionnaire
Contains all 25 survey questions.
Appendix B — Demographic Tables
Contains detailed demographic results.
Appendix C — Statistical Results
Contains extended calculations and tables.
Appendix D — Interview Protocol
Contains the questions used during follow-up interviews.
The main report could then say:
“The complete survey instrument is available in Appendix A.”
That one sentence gives readers a clear path to the supporting evidence.
This is the real purpose of appendices: they preserve detail without allowing detail to bury the main argument.
How to Remember Appendices vs Appendixes
Here’s an easy way to remember the difference.
Appendices has the traditional -ices ending.
Think:
Appendix → Appendices
Appendixes uses a more familiar English plural ending.
Think:
Appendix → Appendixes
The important memory trick isn’t deciding that one is right and the other is wrong.
Instead, remember:
Both are plural. Both can mean more than one appendix.
If you’re writing a formal academic document, appendices is often the natural choice. If your preferred style accepts appendixes, that form works too.
Appendices vs Appendixes: Quick Comparison
| Question | Answer |
| What is the singular? | Appendix |
| What is the traditional plural? | Appendices |
| Is appendixes correct? | Yes |
| Do both plurals refer to multiple appendices? | Yes |
| Is appendices common in academic writing? | Yes |
| Can you use appendixes in US English? | Yes |
| Should you mix the two forms? | Usually avoid it |
| Should you follow a required style guide? | Yes |
| Does appendix also have an anatomical meaning? | Yes |
FAQs
1. Are appendices and appendixes both correct?
Yes. Appendices and appendixes are both accepted plural forms of appendix. Appendices has a longer history in English, but appendixes is also correct and commonly used today.
2. Which form is preferred in academic writing?
Appendices is traditionally common in academic writing, especially in research papers, reports, and formal documents. However, appendixes can also be correct if it matches the required style guide or institutional preference.
3. What is the plural of appendix in medical writing?
In medical writing, both appendices and appendixes can refer to more than one appendix. The choice depends on the publication’s preferred usage and style.
4. Why are there two plural forms of appendix?
The two forms developed because appendix is a foreign-derived word. English has gradually Anglicized the plural of many borrowed words, creating forms such as appendixes alongside the older appendices.
5. Should I use appendices or appendixes in one document?
Choose one form and use it consistently throughout the document. Checking your dictionary, publisher, school, or organization’s style rules can help you make the appropriate choice and avoid inconsistency.
Conclusion
Understanding Appendices vs Appendixes is mainly about recognizing that both forms are correct while paying attention to context, usage, and consistency. Appendices is the traditional plural and remains common in academic writing, publishing, research papers, and formal documentation, while appendixes reflects the natural Anglicized development of English. Knowing this difference helps writers, students, and professionals avoid common grammar mistakes without getting stuck on the idea that one form must always be wrong.
For practical writing, the simplest approach is to follow the relevant style guide and use the same plural form throughout your report, book, or research document. Whether you’re discussing medical material or additional sections at the end of a document, consistent usage makes your writing more clear, professional, and confident. Once you understand why these two forms exist, choosing between appendices and appendixes becomes much less confusing.
