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

Under the new-ish Big Data + Panel scheme, regular-season NFL ratings are up 7% versus the year-ago period, while an expansion of the company’s OOH panel ensures that even more Thanksgiving impressions will be totted up after the dust clears down in Arlington. —Anthony Crupi, Sportico.com, 26 Nov. 2025

The expansion will include a new golf line under the brand, and the three-time Super Bowl champion is set to remain a key figure in brand campaigns, building on collaborations with other global stars such as Lionel Messi and Kaka. —Cole Sullivan, MSNBC Newsweek, 26 Nov. 2025

This all changed in the late 1800s when buffalo and Blackfeet people were targeted amid Westward expansion in the United States. —Alexandra Schonfeld, PEOPLE, 26 Nov. 2025

The company shuttered its initial Prime Air site in Lockeford, California, in 2024, but has continued operations in College Station, Texas, and Tolleson, Arizona, with more recent expansions into areas like Kansas City, Missouri, San Antonio Texas, and Ruskin, Florida. —Meghan Hall, Sourcing Journal, 26 Nov. 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