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

• 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

Biglari’s core demands were to stop opening new stores entirely, eliminate the development team to save money, and focus exclusively on improving existing store operations rather than expansion. —Lily Mae Lazarus, Fortune, 18 Sep. 2025

Marvel Avengers Expansion Impressions The biggest strength of the Marvel Multiverse Role Playing Game expansions continues to be succinct writing that pares down decades of comic book history into a short but informative chapter. —Rob Wieland, Forbes.com, 17 Sep. 2025

Some of those plans include terminal lobby expansions, concourse upgrades, and traffic improvements. —Chase Jordan, Charlotte Observer, 17 Sep. 2025

The company remains optimistic about its expansion plans even amid concerns over the potential impact of tariffs on discount retailers like Primark, which relies heavily on imports and operates on thin margins. —Hugh Cameron, MSNBC Newsweek, 17 Sep. 2025

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