Appendices or Appendixes: Which Is Correct?

Updated 2026-10-12 · Which One Is Correct editorial team

Quick answer: When deciding between appendices and appendixes, the choice depends entirely on what you are describing. Both forms are grammatically correct plurals of the word appendix, yet they serve different purposes. Use appendices when referring to the supplementary sections at the end of a book or report. Conversely, use appendixes when discussing the human body parts or organs.

The Short Answer

Both plurals of appendix are accepted, but appendices is the Latin-style form common for sections added to books, while appendixes is the English plural often used for the body part.

Confusion arises because the root word sounds identical in both contexts, making it easy to swap them without thinking. Writers often follow the style of their specific field, where science might prefer the Latin form while anatomy uses the English plural.

Side-by-Side Comparison

Form	Status	Use it when
Appendices	Accepted	Sections added to books, reports, or papers.
Appendixes	Accepted	The body parts or organs located in the abdomen.
Appendices	Noun	Plural form for supplementary material.
Appendixes	Noun	Plural form for anatomical structures.

Correct Example Sentences

The student checked the appendices for the extra data charts.
The doctor noted that the appendixes were visible on the scan.
Please review all appendices before submitting the final draft.
Human anatomy textbooks often discuss the appendixes of the digestive system.
The author included three appendices to explain the methodology.
Do not forget to list the appendixes in your inventory report.
Our legal team added two appendices to the contract.
The surgeon removed the appendixes from the patient safely.
Every research paper should have clear appendices attached.
The appendixes of the car manual contain wiring diagrams.

Common Mistakes and Fixes

The report contains appendixes with extra graphs.: The report contains appendices with extra graphs.
I need to find the appendixes in the file.: I need to find the appendices in the file.
Please read the appendixes for the answers.: Please read the appendices for the answers.
The human body has two appendixes.: The human body has two appendixes.
These documents include appendixes for context.: These documents include appendices for context.
The appendixes listed are not necessary.: The appendices listed are not necessary.

Related Word Pairs

Phonemes: Phonemes are speech sounds, not letters
Algebra: Algebra deals with symbols and rules for solving equations
Bacteria: Bacteria are single-celled microorganisms
Data: Data is plural of datum and refers to facts or information
Criterion: Criterion is singular, criteria is plural
Analysis: Analysis is singular, analyses is plural
Diagnosis: Diagnosis is singular, diagnoses is plural
Focus: Focus is singular, foci is plural

Frequently Asked Questions

Which spelling is more formal for a document?

The spelling appendices is considered more formal and is preferred in academic writing, scientific papers, and official reports that include supplementary sections. Writers should choose this form when describing non-anatomical additions.

When should I use appendixes instead of appendices?

You should use the spelling appendixes specifically when referring to the human body parts or organs. This usage aligns with the English pluralization rules and is standard in medical and biological contexts.

Are both spellings considered correct in modern English?

Yes, both spellings are correct according to major style guides and dictionaries. The choice between them depends on whether you are discussing supplementary material or anatomical structures, not on general grammar rules.

Does the singular word change for these plurals?

The singular word is always spelled appendix regardless of which plural form you choose. You simply add -ices for the Latin style or -es for the English style when making it plural.