addition

noun

ad·​di·​tion ə-ˈdi-shən 

a-

1

: a part added (as to a building or residential section)

The addition expanded the kitchen.

2

: anything or anyone added : increase

The clerk was a recent addition to the staff.

3

: the act or process of adding

a recipe enhanced by the addition of freshly ground pepper

especially : the operation of combining numbers so as to obtain an equivalent simple quantity

schoolchildren learning about addition and subtraction

4

: direct chemical combination of substances into a single product

see also:

in addition in addition to

Synonyms of addition

• extension
• annex

Examples of addition in a Sentence

The children learned addition and subtraction.

The museum's collection includes several new additions.

Recent Examples on the Web

Samuel Boivin | Nurphoto | Getty Images SpaceX became one of the quickest additions ever to the Nasdaq-100 index, setting up a fresh wave of buying from passive investors less than a month after the company's blockbuster public debut. — Yun Li, CNBC, 27 June 2026

Merchandise including counterfeit perfumes, Rolex watches, knockoff Knicks apparel, sunglasses, electronics and Labubus were seized, in addition to $145,000 in cash, police said. — Colin Mixson, New York Daily News, 27 June 2026

Praised by several shoppers for its lightweight feel that’s easily layerable with extra blankets in the fall and winter, this three-piece set is a great addition to any bedroom. — Alicia Geigel, Southern Living, 27 June 2026

In addition, my team and I cover her company’s annual event, Workhuman Live, which attracts researchers like Monahan and practitioners from around the world who are dedicated to putting people first. — Laurel Donnellan, Forbes.com, 26 June 2026

Word History

Etymology

Middle English addicioun, borrowed from Anglo-French addicion, borrowed from Latin additiōn-, additiō, from addi-, variant stem of addere "to add" + -tiōn-, -tiō, suffix of action nouns

First Known Use

14th century, in the meaning defined at sense 1

Phrases Containing addition

• in addition
• in addition to

Rhymes for addition

• admission
• ambition
• attrition
• audition
• clinician
• cognition
• coition
• commission
• condition
• contrition
• dentition
• dismission

Kids Definition

addition

noun

ad·​di·​tion ə-ˈdish-ən 

a-

1

: the result of adding : increase

2

: the act, process, or operation of adding

3

: a part added (as to a building)