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

Most have occurred since the beginning of May, in addition to a surge in strikes on other targets such as port facilities and ships. —Gianluca Mezzofiore, CNN Money, 20 June 2026

In addition to scoring the match’s only goal so far, Czechia leads in shots and chances created. —Andrew Greif, NBC news, 19 June 2026

While these new additions span various sectors, their valuations are heavily reliant on AI capital spending. —Dara-Abasi Ita, Forbes.com, 19 June 2026

All this in addition to her high school diploma achieving the Scholar and Industry diploma designations and graduating with Summa Cum Laude honors. —Garfield Hylton, The Orlando Sentinel, 19 June 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)