expansion

noun

ex·​pan·​sion ik-ˈspan(t)-shən 

1

: expanse

2

: the act or process of expanding

territorial expansion

economic expansion

expansion of the universe

3

: the quality or state of being expanded

4

: the increase in volume of working fluid (such as steam) in an engine cylinder after cutoff or in an internal combustion engine after explosion

5

a

: an expanded part

b

: something that results from an act of expanding

The book is an expansion of a lecture series.

6

: the result of carrying out an indicated mathematical operation : the expression of a function in the form of a series

expansional

ik-ˈspan(t)-sh(ə-)nəl 

adjective

Synonyms of expansion

• increase
• boost
• addition
• gain

Examples of expansion in a Sentence

The league is undergoing expansion.

the expansion of a lecture series into a book

This book is an expansion of a lecture series.

Recent Examples on the Web

Suzuki went on to establish Seven & i Holdings in 2005 and oversaw its expansion into a retail conglomerate. —Reuters 20 Hr Ago, CNN Money, 25 May 2026

Coming out of their successful, predatory expansion process, for example, the Golden Knights accumulated six additional draft picks — including two additional first-round picks — making 13 total picks in their inaugural appearance at the draft. —Thomas Drance, New York Times, 25 May 2026

Just over half of the global increase is from the expansion of rice-growing areas. —Hanqin Tian, Fortune, 25 May 2026

His response was a blitz of regional expansion – in the Bengali, Marathi, Malayalam, Kannada, Telugu languages – that rewired the logic of Indian television. —Naman Ramachandran, Variety, 25 May 2026

Word History

First Known Use

1611, in the meaning defined at sense 1

Phrases Containing expansion

• expansion card
• expansion slot

Rhymes for expansion

• mansion
• scansion

Kids Definition

expansion

noun

ex·​pan·​sion ik-ˈspan-chən 

1

: the act of expanding

2

: the state of being expanded

3

: something expanded or a result of expanding

4

: the result of carrying out indicated mathematical operations

the expansion of (a + b)² is a² + 2ab + b²

Medical Definition

expansion

noun

ex·​pan·​sion ik-ˈspan-chən 

1

: the act or process of expanding

2

: the quality or state of being expanded