addition

American  

[uh-dish-uhn] / əˈdɪʃ ən /

noun

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.

   Synonyms:

   accession, increment, enlargement, increase

4. something added.

   Synonyms:

   appendix, supplement, accession, increment, enlargement, increase

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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idioms

1. in addition to, as well as; besides.

   In addition to directing the play, she designed most of the scenery.

addition British  

/ əˈdɪʃən /

noun

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. a part added to a building or piece of land; annexe

5. obsolete a title following a person's name

6. (adverb) also; as well; besides

7. (preposition) besides; as well as

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addition Scientific  

/ ə-dĭsh′ən /

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

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addition More Idioms  

1. see in addition.

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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.

Related Words

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

• preaddition noun
• readdition noun

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.

Example Sentences

In addition, patients who had more extensive resurfacing regained only about 7 pounds and kept more than 80% of their weight loss.

From Science Daily • Apr. 23, 2026

Ford’s board in addition has changed how it calculates bonuses for Chief Executive Officer Jim Farley and other top executives, according to a recent proxy statement.

From The Wall Street Journal • Apr. 22, 2026

In addition to the increased volatility driven by the Iran war and policy uncertainty, recent market performance has been marked by a large divergence in returns across different sectors of the economy.

From MarketWatch • Apr. 22, 2026

"In addition, we reported this to the Charity Commission in 2024, who reviewed the matter and confirmed that no further action was required."

From BBC • Apr. 22, 2026

Bobby thought he’d easily walk through the Mar Del Plata tournament until he learned that David Bronstein and Fridrik Olafsson were also going to play, in addition to the twenty-three-year-old grandmaster from Leningrad, Boris Spassky.

From "Endgame" by Frank Brady

Related Words

• bonus
• boost
• enhancement
• expansion
• extension
• supplement