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 changes at the intersection will mean the addition of two signs that will have flashing lights triggered by people or traffic at the crossing roads. —Alan Gionet, CBS News, 25 Mar. 2026

Gray Gubler is a producer in addition to starring. —Joe Otterson, Variety, 24 Mar. 2026

In addition to his robust campaign fundraising, Holland has been able to bring on the head of the local Republican Party, Matthew Kay, as his campaign chair. —Richard A. Webster, ProPublica, 24 Mar. 2026

Molly Pierce, a spokesperson for the Oahu Emergency Management Agency, said that in addition to volunteers and public workers who have been cleaning up, a contract company had arrived to begin collecting, sorting and removing large piles of debris. —ABC News, 24 Mar. 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)