[ uh-dish-uhn ]
See synonyms for: additionadditions on

  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 +.

  1. the result of adding.

  2. something added.

  3. a wing, room, etc., added to a building, or abutting land added to real estate already owned.

  4. Chemistry. a reaction in which two or more substances combine to form another compound.

Idioms about addition

  1. in addition to, as well as; besides: In addition to directing the play, she designed most of the scenery.

Origin of addition

First recorded in 1350–1400; Middle English addicio(u)n, from Latin additiōn-, stem of additiō, from addit(us) “added” (past participle of addere “to add”; see add ) + -iō -ion

synonym study For addition

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.

Other words for addition

Other words from addition

  • pre·ad·di·tion, noun
  • re·ad·di·tion, noun

Words that may be confused with addition

Words Nearby addition Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2024

How to use addition in a sentence

British Dictionary definitions for addition


/ (əˈdɪʃən) /

  1. the act, process, or result of adding

  2. a person or thing that is added or acquired

  1. a mathematical operation in which the sum of two numbers or quantities is calculated. Usually indicated by the symbol +

  2. mainly US and Canadian a part added to a building or piece of land; annexe

  3. obsolete a title following a person's name

  4. in addition (adverb) also; as well; besides

  5. in addition to (preposition) besides; as well as

Origin of addition

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

Scientific definitions for addition


[ ə-dĭshən ]

  1. The act, process, or operation of adding two or more numbers to compute their sum.

The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

Other Idioms and Phrases with addition


see in addition.

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