[ uh-den-duhm ]
See synonyms for addendum on
noun,plural ad·den·da [uh-den-duh] /əˈdɛn də/ for 1, 2; ad·den·dums for 3.
  1. a thing to be added; an addition.

  2. an appendix to a book.

  1. Machinery.

    • the radial distance between the tip of a gear tooth and the pitch circle of a gear or the pitch line of a rack.: Compare dedendum.

    • Also called addendum circle. an imaginary circle touching the tips of the teeth on a gear.

Origin of addendum

First recorded in 1785–95; neuter singular of Latin addendus “that which is to be added,” gerundive of addere “to add”; see add

Words Nearby addendum Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use addendum in a sentence

British Dictionary definitions for addendum


/ (əˈdɛndəm) /

nounplural -da (-də)
  1. something added; an addition

  2. a supplement or appendix to a book, magazine, etc

  1. the radial distance between the major and pitch cylinders of an external screw thread

  2. the radial distance between the pitch circle and tip of a gear tooth

Origin of addendum

C18: from Latin, literally: a thing to be added, neuter gerundive of addere to add

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012