appendix

American  

[uh-pen-diks] / əˈpɛn dɪks /

noun

plural

appendices, appendixes

1. supplementary material at the end of a book, article, document, or other text, usually of an explanatory, statistical, or bibliographic nature.

   Synonyms:

   supplement, addition, appurtenance, adjunct, addendum

2. an appendage.

3. Anatomy.

   1. a process or projection.

   2. the vermiform appendix.

4. Aeronautics. the short tube at the bottom of a balloon bag, by which the intake and release of buoyant gas is controlled.

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appendix British  

/ əˈpɛndɪks /

noun

1. a body of separate additional material at the end of a book, magazine, etc, esp one that is documentary or explanatory

2. any part that is dependent or supplementary in nature or function; appendage

3. anatomy See vermiform appendix

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appendix Scientific  

/ ə-pĕn′dĭks /

plural

appendixes

1. A tubular projection attached to the cecum of the large intestine and located on the lower right side of the abdomen.

2. Also called vermiform appendix

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appendix Cultural  

1. A small saclike organ located at the upper end of the large intestine. The appendix has no known function in present-day humans, but it may have played a role in the digestive system in humans of earlier times. The appendix is also called the vermiform appendix because of its wormlike (“vermiform”) shape.

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Spelling

Appendices, a plural borrowed directly from Latin, is the usual plural, especially in scholarly writing, when referring to supplementary material at the end of a book. Appendixes is the usual plural in the anatomical meaning.

Usage

Plural word for appendix The plural form of appendix can be either appendices, pronounced [ uh-pen-duh-seez ], or appendixes, but appendices is more widely used. The plural forms of several other singular nouns that end in -ix or -ex are also formed in this way, such as index/indices, matrix/matrices, and codex/codices.  Irregular plurals that are formed like appendices derive directly from their original pluralization in Latin. However, the standard English plural -es is often also acceptable for these terms, as in indexes and matrixes.

Related Words

Appendix, supplement both mean material added at the end of a book. An appendix gives useful additional information, but even without it the rest of the book is complete: In the appendix are forty detailed charts. A supplement, bound in the book or published separately, is given for comparison, as an enhancement, to provide corrections, to present later information, and the like: A yearly supplement is issued.

Etymology

Origin of appendix

First recorded in 1535–45; from Latin: literally, “appendage,” equivalent to append(ere) “to add on” + -ix (equivalent to -ic- noun suffix + -s nominative singular ending); append

Example Sentences

She waited four months before her appendix could be removed.

From BBC • Mar. 16, 2026

The appendix notes: “We need definitive RCT data to determine whether whole-fat dairy intake will improve the metabolic health of American children.”

From Slate • Jan. 28, 2026

The plagiarised work now finds its place in an appendix to the forthcoming collection Dylan Thomas - The Complete Poems.

From BBC • Jan. 8, 2026

If instituting fair grades leads to crying, sobbing and “soul-crushing” setbacks, I wish her luck should she ever be called on to dig out a ruptured appendix at 3 a.m. on her birthday.

From The Wall Street Journal • Nov. 4, 2025

“Good. Good. I told you this is a fine hospital. Had my appendix out here.”

From "The Chosen" by Chaim Potok

Related Words

• addendum
• postscript