addendum

noun

ad·​den·​dum ə-ˈden-dəm 

plural addenda ə-ˈden-də  also addendums

1

: a thing added : addition

2

: a supplement to a book

—often used in plural but singular in construction

Synonyms of addendum

• appendix

Examples of addendum in a Sentence

Francine du Plessix Gray, in an essay first written in 1991 and updated with an addendum here, writes eloquently of a lifelong obsession with weight loss, stemming from the harsh judgments of a mother enraptured by fashion. —Ginia Bellafante, New York Times Book Review, 21 Sept. 2008

This qualification, however, is not a recent addendum to Derrida's career. In 1990, near the end of the period in which rhetoric and composition had a strong interest in his work, Derrida participated in an editor's interview … in which he characterized his project as fundamentally tied to the tradition it works both within and against. —College English, September 2006

The letters are included as an addendum to the biography.

there's an addendum from the author to explain certain stylistic choices that she made

Recent Examples on the Web

During discussions about elementary and middle school social studies curriculum, board members made addendums, including education about the horrors of communism, why the Second Amendment was created and how counterculture increased the rate of divorce. — Rachel Royster, Fort Worth Star-Telegram, 27 June 2026

The horrifying addendum was that her two-year-old son was the only witness to the crime, and had to draw on limited memory and communication skills to try and convey details about the murderer, who was, in fact, caught and convicted 16 years later. — Paul Tassi, Forbes.com, 9 June 2026

While the Brooklynite was more of an addendum than a star in that book, its a delightful little drink and among the better things to make with a bottle of Jamaican rum. — Jeremy Repanich, Robb Report, 6 June 2026

Advertisement Blanche defended the tax term, which had been included in an addendum to the DOJ’s announcement of the fund and not separately announced. — Miranda Jeyaretnam, Time, 3 June 2026

Word History

Etymology

borrowed from Latin, neuter of addendus, gerundive of addere "to add"

First Known Use

1664, in the meaning defined at sense 1

Rhymes for addendum

• corrigendum
• sedum

Kids Definition

addendum

noun

ad·​den·​dum ə-ˈden-dəm 

plural addenda -ˈden-də 

: something added (as to a book)