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

An addendum was released earlier this year focused on parks and schools to determine whether pesticides were reaching public spaces. — Christiana Freitag, Chicago Tribune, 16 Aug. 2026

Developers are arguing that an environmental impact report is unnecessary because of an outdated assessment from 2002 and an addendum from 2012. — Veronica Eady, Mercury News, 14 Aug. 2026

In a company addendum to the report, which did not identify its author, Blackbird appeared to rebut those questions. — Andrew Graham, Sacbee.com, 10 Aug. 2026

This little addendum—that politics mean nothing to the Bret Easton Ellis of 2023—is eminently untrue, as anyone who has listened to his podcast, which often turns to political commentary, will attest. — Leo Lasdun, New Yorker, 5 Aug. 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)