addition
Americannoun
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the act or process of adding or uniting.
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the process of uniting two or more numbers into one sum, represented by the symbol +.
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the result of adding.
- Synonyms:
- accession, increment, enlargement, increase
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something added.
- Synonyms:
- appendix, supplement, accession, increment, enlargement, increase
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a wing, room, etc., added to a building, or abutting land added to real estate already owned.
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Chemistry. a reaction in which two or more substances combine to form another compound.
idioms
noun
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the act, process, or result of adding
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a person or thing that is added or acquired
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a mathematical operation in which the sum of two numbers or quantities is calculated. Usually indicated by the symbol +
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a part added to a building or piece of land; annexe
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obsolete a title following a person's name
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(adverb) also; as well; besides
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(preposition) besides; as well as
Usage
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.
Synonym Usage
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 Word Forms
Derived Forms
Inflected Forms
Nouns
Etymology
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
Explanation
An addition is the act of adding something new, like a baby — a new addition to your family — or what you do in math class: the addition of columns of numbers to get the sum. The noun addition comes from the Old French word adition, meaning "that which is added." A new room built onto your house, a new item in a store's inventory, even another baseball cap in your collection — all of these are additions. Usually thought of as improvements, you may have heard the phrase "welcome addition" to describe a new cast mate to a television show that has lost its creative spark or a new ball field at your local park.
Vocabulary lists containing addition
Arithmetic
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List 1
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The Number System
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Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
See Examples For:
The maker of spices and seasonings said Thursday that the London listing would come in addition to its current listing on the New York Stock Exchange.
From The Wall Street Journal ● Jul. 23, 2026
In addition to the anti-ball playing ordinance, the neighbors were accused of violating an ordinance prohibiting structures on sidewalks or grassy strips next to curbs.
From Los Angeles Times ● Jul. 23, 2026
It says this will be used in addition to funds already earmarked by the Department for Transport for buses.
From BBC ● Jul. 22, 2026
In addition to orchestrating different AI models, the AI Control Tower is now increasingly serving as a gateway to vet nonhuman identities.
From MarketWatch ● Jul. 22, 2026
He was told that in addition to enemy fighters, about two thousand people lived and fished in the area they’d flown over.
From "Most Dangerous: Daniel Ellsberg and the Secret History of the Vietnam War" by Steve Sheinkin
For the full year, T-Mobile continues to guide for 950,000 to 1.05 million postpaid net account additions.
From The Wall Street Journal ● Jul. 23, 2026
They included legislative educational additions such as ethnic studies and financial literacy, a statewide push into college and career pathways, and the expansion of dual enrollment with community colleges.
From Los Angeles Times ● Jul. 23, 2026
The company reported 432,000 postpaid phone net additions for the second quarter, with the figure tracking customers who pay for phone service after each cycle is complete.
From MarketWatch ● Jul. 22, 2026
Kiernan would bring attacking depth to Newcastle, who have had a busy transfer window with six additions as they prepare to challenge for the WSL 2 title.
From BBC ● Jul. 22, 2026
The concrete additions look harsh against the softer colors of the original house, but that’s how most homes look in Los Ojos—a clumsy mix of old and new.
From "I Am Not Your Perfect Mexican Daughter" by Erika L. Sánchez
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
