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

The research, conducted by Pranay Mudaliar and Jerin John, an associate professor of mechanical, industrial and aerospace engineering at Concordia University, examines how the gel responds to shear, temperature, and the addition of ethanol. — Maria Mocerino, Interesting Engineering, 2 Nov. 2026

The sommelier was knowledgeable and provided us with pairings that spanned traditional offerings like cheeses, as well as some surprising additions like home fries and oxtail. — Condé Nast, Condé Nast Traveler, 2 Nov. 2026

First there was LeBron James positing in the wake of the addition of Giannis Antetokounmpo. — Ira Winderman, Sun Sentinel, 1 Nov. 2026

That addition is The Horseshoe bar, a nightclub country bar that’s attached to five nightlife concepts — Bar Rec, The Landing, Jungalow, Uncle Jim’s and The Patio. — Katelyn Umholtz, Kansas City Star, 30 Oct. 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)