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

The airline also opened a flight attendant base in Austin in October and expects to control 15 gates once a major expansion at Austin-Bergstrom is completed in the early 2030s. —Alex Driggars, Austin American Statesman, 21 Mar. 2026

That rise in traditional TV is not expected to continue over the longer term, Nielsen has indicated, but streaming’s expansion is. —Brian Steinberg, Variety, 20 Mar. 2026

House Bill 913 would thrust new three-month work requirements onto adult Medicaid expansion recipients to maintain their health care coverage — the maximum allowed under federal legislation passed last year to be enrolled in the program. —Kevin Fixler, Idaho Statesman, 20 Mar. 2026

The order reflects the concerns over the expansion of the College Football Playoffs and the possibility of those games competing for the attention of viewers. —Ted Johnson, Deadline, 20 Mar. 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