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 headliner specs on it are an 8,000-mAh battery, 45-W fast-charging, a MediaTek Dimensity 7025 CPU, 12 GB of RAM, 512 GB of internal storage, and microSD expansion up to 2 TB. — Joe Salas july 26, New Atlas, 27 July 2026

San Diego, an expansion team last season, played Dallas to a 3-3 draw in Texas in mid-March and is 3-0-1 in the first four matchups. — ABC News, 26 July 2026

At the time, Larson had just won an Oscar for Room, and her casting seemed to point to an expansion of who Marvel movies were about. — Hannah Abraham, Forbes.com, 26 July 2026

The third-priciest project submitted to the task force is another expansion of the Orange County Convention Center, now the nation’s third-largest visitors’ complex behind McCormick Place in Chicago and the Las Vegas Convention Center. — Ryan Gillespie, The Orlando Sentinel, 26 July 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