• synonyms


  1. a plural of addendum.
  2. (used with a singular verb) a list of things to be added: The addenda in the back of the book runs to thirty pages.
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[uh-den-duh m]
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.
  3. Machinery.
    1. 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.
    2. Also called addendum circle.an imaginary circle touching the tips of the teeth on a gear.
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Origin of addendum

1785–95; neuter singular of Latin addendus to be added, gerundive of addere to add
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Related Words


Examples from the Web for addenda

Historical Examples

  • The receipts will be found in the Addenda, under the head of Hospital Diets.

    Soyer's Culinary Campaign

    Alexis Soyer

  • Where then, it may be asked, are the addenda to be placed at the end of each century?

  • The correction, revision, and addenda do not call for any special notice.

  • In calculating the addenda of bills she frequently had recourse to digital aid.


    James Joyce

  • These addenda in the colonel's own handwriting tickled Norton's fancy.

    Sons and Fathers

    Harry Stillwell Edwards

British Dictionary definitions for addenda


noun plural -da (-də)
  1. something added; an addition
  2. a supplement or appendix to a book, magazine, etc
  3. the radial distance between the major and pitch cylinders of an external screw thread
  4. the radial distance between the pitch circle and tip of a gear tooth
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Word Origin

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

Word Origin and History for addenda



1794, literally "something added," from Latin addendum, neuter of addendus "that which is to be added," gerundive of addere (see add (v.)). Classical plural form is addenda.

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Online Etymology Dictionary, © 2010 Douglas Harper