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

• 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

Although cancer of the appendix is rare – typically, it’s estimated to affect about 1 or 2 people for every 1 million in the United States each year – diagnoses are rising sharply among Generation X and millennials, according to a new study. —Jacqueline Howard, CNN Money, 15 June 2025

Appendix cancer is often found after someone has appendicitis and gets their appendix removed. —Kristen Fischer, Health, 13 June 2025

Appendiceal cancer forms in the appendix, which is a small organ located in the lower right abdomen. —Melissa Rudy, FOXNews.com, 10 June 2025

In a new report, published in the Annals of Internal Medicine, researchers at Vanderbilt University focus on a relatively rare cancer—appendiceal cancer, which occurs in the appendix—and found that its rates are also rising, especially among millennials. —Alice Park, Time, 9 June 2025

Word History

Etymology

Latin appendic-, appendix, from appendere — see append

First Known Use

1542, in the meaning defined at sense 1a

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