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

The Martins and former group member Andre Thomas, 48, have also been charged with the killing of 4-year-old Timothy Thomas, who was found dead of septic shock caused by a ruptured appendix at one of the group’s properties in Colton in 2010. —Clara Harter, Los Angeles Times, 17 Jan. 2026

The appendix acts a safe house for beneficial gut bacteria that help repopulate the digestive system after illness. —Scott Lafee, San Diego Union-Tribune, 13 Jan. 2026

Treatment for the condition generally involves antibiotics and surgical removal of the appendix, per Mayo Clinic. —Rachel Raposas, PEOPLE, 8 Jan. 2026

According to the accompanying appendix, which outlined the accusations and was under seal until Tuesday, Remington penned the bulk of Hyland’s opinion denying the defense’s dismissal motion, constituting a clear breach of Wisconsin’s judicial code of conduct. —Mia Cathell, The Washington Examiner, 11 Dec. 2025

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