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 Vikings will be banking on him and the rest of their new defensive line additions to maintain the performance that has anchored the defense since Flores arrived in 2023. —Jeff Howe, New York Times, 25 Apr. 2026

Another passable addition to my Pretend Happy Hour routine. —Alex Beggs, Bon Appetit Magazine, 25 Apr. 2026

In addition to the sapphire engagement ring worn by Kate and Diana (both of whom held the Princess of Wales title) and the diamonds in Meghan's engagement ring that used to belong to Diana, the two women have been seen in other sentimental pieces of the late Princess's jewelry. —Stephanie Petit, PEOPLE, 24 Apr. 2026

In addition, the right side of the jaws tended to be more worn down than the left side. —Ari Daniel, NPR, 24 Apr. 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)