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 containing marine collagen sourced from fish, this powder features vitamin C from acerola cherry and silicon from bamboo, the latter of which helps provide strength and structure to hair, skin, and nails. —Emily Orofino, Vogue, 4 Mar. 2026

In addition to the void left by Lemon and Lane’s departures, the Trojans will also be without their top returning wideout this spring, as Tanook Hines will sit out the entire session following an offseason procedure. —Ryan Kartje, Los Angeles Times, 4 Mar. 2026

Accessibility The InterContinental has accessible routes, wheelchair-accessible rooms (with options for roll-in showers), and visual alarms, in addition to accessible parking, a pool hoist, braille signage, and accessible meeting rooms. —Condé Nast, Condé Nast Traveler, 4 Mar. 2026

In addition to extinguishing fires, the Unmanned Firefighting Robot can collect and digitize data from disaster scenes. —Atharva Gosavi, Interesting Engineering, 4 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)