appendix

noun

ap·​pen·​dix ə-ˈpen-diks 

plural appendixes or appendices ə-ˈpen-də-ˌsēz 

1

a

: appendage

b

: supplementary material usually attached at the end of a piece of writing

The book's appendix includes a bibliography.

2

: a bodily outgrowth or process

specifically : vermiform appendix

Synonyms of appendix

• epilogue
• supplement
• documentation
• afterword
• addition
• addendum
• codicil
• conclusion

Examples of appendix in a Sentence

In your textbooks, turn to Appendix 3: Glossary of Terms.

The book has several appendixes.

Recent Examples on the Web

Gore died last month following complications after emergency surgery to have his appendix removed. —Pete Grathoff, Kansas City Star, 30 Mar. 2026

Swalwell was among those named by Patel, who has said that his critics are mischaracterizing the appendix by calling it an enemies list. —Perry Stein The Washington Post, Arkansas Online, 29 Mar. 2026

An inflamed appendix becomes a ruptured one, leading to systemic infection. —Dr. Lauren Palladino, Hartford Courant, 22 Mar. 2026

Amanda Gushue, 37, first visited her primary care physician — who sent her to the emergency department (ED) with a swollen appendix. —Melissa Rudy, FOXNews.com, 16 Mar. 2026

Word History

Etymology

borrowed from Latin appendic-, appendix "something subordinate or supplementary attached to a larger unit," fr. appendere, presumably "to attach to something larger by hanging " + -ic-, -ix, noun suffix — more at append

Note: Regarding the meaning of appendere see note at append.

First Known Use

1549, in the meaning defined at sense 1b

Phrases Containing appendix

• vermiform appendix

Kids Definition

appendix

noun

ap·​pen·​dix ə-ˈpen-diks 

plural appendixes or appendices -də-ˌsēz 

1

: additional material attached at the end of a piece of writing

2

: a small tube that is closed at one end and projects from the pouch marking the beginning of the large intestine in the lower right side of the abdomen

Medical Definition

appendix

noun

ap·​pen·​dix ə-ˈpen-diks 

plural appendixes or appendices -də-ˌsēz 

: a bodily outgrowth or process

specifically : vermiform appendix