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

Build a Command Deck With the Control Center The Control Center was a welcome addition to iOS 7 in 2013, but its implementation still feels more like a junk drawer than a command center. — Florence Ion, PC Magazine, 20 Sep. 2026

Speaking of dominating running backs, Kenneth Walker III, who came over from the Seahawks after winning Super Bowl MVP, looked like the best offseason addition. — Outkick, FOXNews.com, 20 Sep. 2026

The pool on the roof is an optimistic addition in the face of Milan’s often gray climate. — Hamish Bowles, Vogue, 20 Sep. 2026

If your family loves bacon, double it and make the whole pound for a generous addition to each bowl. — Erin Merhar, Southern Living, 19 Sep. 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)