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

In addition to Slattery, Mardie Frye, Charlie Watson and Jayde Hudson scored goals in the shootout for Centennial. —Darren Lauber, Fort Worth Star-Telegram, 1 Apr. 2026

Add remaining meringue in 3 batches, gently folding with a rubber spatula after each addition until only a few streaks of meringue remain (err on the side of undermixing to keep the cake batter billowy). —Shilpa Uskokovic, Bon Appetit Magazine, 1 Apr. 2026

In addition, motions in which the prosecution opposed mental health diversions for two defendants contained similar errors, Stuart wrote. —Sharon Bernstein, Sacbee.com, 1 Apr. 2026

In addition, the system’s design and control software are entirely based on proprietary technology. —Jijo Malayil, Interesting Engineering, 31 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)