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See more synonyms for addition on Thesaurus.com
  1. the act or process of adding or uniting.
  2. the process of uniting two or more numbers into one sum, represented by the symbol +.
  3. the result of adding.
  4. something added.
  5. a wing, room, etc., added to a building, or abutting land added to real estate already owned.
  6. Chemistry. a reaction in which two or more substances combine to form another compound.
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  1. in addition to, as well as; besides: In addition to directing the play, she designed most of the scenery.
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Origin of addition

1350–1400; Middle English addicio(u)n < Latin additiōn- (stem of additiō), equivalent to addit(us), past participle of addere to add (ad- ad- + di- put + -tus past participle suffix) + -iōn- -ion
Related formspre·ad·di·tion, nounre·ad·di·tion, noun
Can be confusedaddition edition


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Synonym study

4. Addition, accessory, adjunct, attachment mean something joined onto or used with something else. Addition is the general word, carrying no implication of size, importance, or kind, but merely that of being joined to something previously existing: an addition to an income, to a building, to one's cares. An accessory is a subordinate addition to a more important thing, for the purpose of aiding, completing, ornamenting, etc.: accessories to a costume. An adjunct is a subordinate addition that aids or assists a main thing or person but is often separate: a second machine as an adjunct to the first. An attachment is an accessory part that may be easily connected and removed: a sewing machine attachment for pleating.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Related Words


Examples from the Web for addition

Contemporary Examples

Historical Examples

  • I have another favour to ask, in addition to the many claims you already have upon me.


    Lydia Maria Child

  • But the family-party was soon to be broken up—not by subtraction, but by addition.

    Weighed and Wanting

    George MacDonald

  • In addition, there were as many of books and magazines as she could wish.

    Within the Law

    Marvin Dana

  • In addition, these vegetables may be combined in almost any way.

    Woman's Institute Library of Cookery, Vol. 4

    Woman's Institute of Domestic Arts and Sciences

  • The same singers, with the addition of Anastasia Robinson, appeared in the season of 1721-22.


    Edward J. Dent

British Dictionary definitions for addition


  1. the act, process, or result of adding
  2. a person or thing that is added or acquired
  3. a mathematical operation in which the sum of two numbers or quantities is calculated. Usually indicated by the symbol +
  4. mainly US and Canadian a part added to a building or piece of land; annexe
  5. obsolete a title following a person's name
  6. in addition (adverb) also; as well; besides
  7. in addition to (preposition) besides; as well as
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Word Origin

C15: from Latin additiōn-, from 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 addition


late 14c., "action of adding numbers;" c.1400, "that which is added," from Old French adition "increase, augmentation" (13c.), from Latin additionem (nominative additio) "an adding to, addition," noun of action from past participle stem of addere (see add). Phrase in addition to "also" is from 1681.

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Online Etymology Dictionary, © 2010 Douglas Harper

addition in Science


  1. The act, process, or operation of adding two or more numbers to compute their sum.
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The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

Idioms and Phrases with addition


see in addition.

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The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.