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

The expansion will also include more language support, with plans to increase access to consulting and capital assistance in Spanish and Marshallese, according to an organization news release. —Arkansas Online, 11 Sep. 2025

Sacred Heart Schools announced a sweeping expansion to the Sacred Heart Academy campus focused on improving student facilities, expanding endowments to support scholarships and strengthening the school's annual fund. —Ray Padilla, The Courier-Journal, 10 Sep. 2025

The expansion is being fueled by its cloud infrastructure business as demand for AI is showing no signs of letting up. —Bloomberg, Mercury News, 10 Sep. 2025

Investment will be directed toward new product development and support for its upcoming wholesale retail expansion into 1,300 doors across two undisclosed chains. —Emma Sandler, Forbes.com, 10 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