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 capital will also support geographic expansion. —Sarah Jones, Sourcing Journal, 15 Aug. 2025

The new location is in Tamarac, in a retail center at Commercial Boulevard and University Drive, anchored by Publix. CEO and founder Chris Johnson says demographics are driving the company’s expansion in the state. —Cindy Krischer Goodman, Sun Sentinel, 15 Aug. 2025

Belmont University's Mike Curb College of Entertainment and Music Business has opened the first of two phases of its $58 million Music Row expansion. —Marcus K. Dowling, The Tennessean, 15 Aug. 2025

Tennessee's statewide expansion to its controversial voucher program included one-time $2,000 bonuses for teachers. —Rachel Wegner, Nashville Tennessean, 15 Aug. 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