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:
In addition, U.S. officials were working Sunday to try to identify additional human remains found at the site in Jordan as a third servicemember remained missing following the attack.
From The Wall Street Journal ● Jul. 20, 2026
"In addition, the process generates numerous transformation products that we have not yet been able to investigate in detail -- for instance, gaseous compounds that form during the reaction."
From Science Daily ● Jul. 20, 2026
“In addition, the physical nature of these experiences should be insulated from AI disruption relative to other services offerings.”
From MarketWatch ● Jul. 20, 2026
In addition to the Mommy and Me tennis class, Roman takes private tennis lessons.
From Los Angeles Times ● Jul. 20, 2026
In addition, Shackleton allowed hot milk and sugar at regular intervals: the only way to keep going was by fueling themselves constantly.
From "Shipwreck at the Bottom of the World" by Jennifer Armstrong
The fundamental backdrop also remains constructive because “meaningful” chip supply additions are not likely due before 2028, they added.
From MarketWatch ● Jul. 20, 2026
Nathan Berman, managing principal and founder of MetroLoft, said that the steel columns may have buckled because they hadn’t been properly reinforced to support the extra weight of the new additions to the property.
From The Wall Street Journal ● Jul. 14, 2026
People will be more likely to become parents if they sense that children will be fun and meaning-making additions to an already full existence, not the beginning of an end to the lives they’ve created.
From Slate ● Jul. 6, 2026
The northern region, which Woodard calls "Yankeeland", is rooted in the early Puritan settlers who fled religious persecution in Europe, with later additions of Germans and Scandinavian settlers helping to solidify a pluralistic outlook.
From BBC ● Jul. 4, 2026
The newer ones—the latest additions the men put up now that the corn was picked—followed an identical style, with more spacious rooms, and were distributed on the property with more care.
From "The Underground Railroad: A Novel" by Colson Whitehead
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.
