[ uh-dish-uhn ]
/ əˈdɪʃ ən /
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See synonyms for: addition / additions on Thesaurus.com

the act or process of adding or uniting.
the process of uniting two or more numbers into one sum, represented by the symbol +.
the result of adding.
something added.
a wing, room, etc., added to a building, or abutting land added to real estate already owned.
Chemistry. a reaction in which two or more substances combine to form another compound.
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Idioms about addition

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

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

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.


pre·ad·di·tion, nounre·ad·di·tion, noun


addition , edition
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023


What is a basic definition of addition?

Addition is a mathematical operation in which two or more numbers are combined to equal a greater number. The word addition also refers to the act of adding. More generally, it refers to an increase or boost applied to something. Addition has a few other senses as a noun.

Addition is one of math’s basic operations. Two or more numbers are united to result in a greater number, called a sum. The symbol used for addition is +, which is called a plus sign.

Real-life examples: Here are some basic examples of addition: 2 + 2 = 4, 17 + 35 = 52, 143 + 64 = 207.

Used in a sentence: I’m teaching the kids to use addition to figure out how much money they need to pay for lunch. 

An addition is something that has been joined or combined with something else to enhance it or provide more to it.

Real-life examples: Recipes can be improved or made more flavorful by using additions such as spices. Accessories and decorations are used as additions to things like cars or clothing to make them look nicer or more stylish.

Used in a sentence: Paintings and flowers make nice additions to any room. 

Relatedly, addition can refer to new rooms or wings that are attached to a building.

Used in a sentence: The college is planning a new addition to the campus library. 

Addition is also used to refer to the act or an instance of adding to something or increasing it in some way.

Used in a sentence: The roller coaster became much more popular after the addition of exciting music and amazing decorations.

Where does addition come from?

The first records of the word addition come from around 1350. It ultimately comes from the Latin additiōn-, which comes from the verb addere, meaning “to add.”

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What are some other forms related to addition?

  • preaddition (noun)
  • readdition (noun)

What are some synonyms for addition?

What are some words that share a root or word element with addition

What are some words that often get used in discussing addition?

What are some words addition may be commonly confused with?

How is addition used in real life?

Addition is a common word used in the context of math and in general.



Try using addition!

Is the following math problem an example of addition?

5 x 6 = 30

How to use addition in a sentence

British Dictionary definitions for addition

/ (əˈdɪʃən) /


Word Origin for 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 ]

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.