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

Rooms Just 66 rooms sit within the hotel's original 1926 structure, and 144 more in the more modern, glassy addition jut out the rear to bring the total count to 210. —Condé Nast, Condé Nast Traveler, 23 May 2026

The addition is expected to expand access to around 125 more students and 30 employees over seven years. —Kate Perez, Chicago Tribune, 23 May 2026

Gemma Chan wears a stunning black gown with a lace addition to the Soccer Aid For UNICEF Gala presented by EA Sports FC on May 21 in London. —People Staff, PEOPLE, 22 May 2026

In addition to Tarabay and Davis, the cast also includes Graham McTavish, Jordi Webbe, Jamaica Vaughan, Ivana Baquero, Claudia Black as Cossutia, India Shaw-Smith, Jackson Gallagher, Jaime Slater, and Leigh Gill. —Rosy Cordero, Deadline, 22 May 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)