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

With hopes to relieve the congestion concerns, leadership at the Port of Antwerp-Bruges has said the recent disruptions have accelerated plans for about $6 billion in capacity expansion projects throughout the gateway. —Glenn Taylor, Footwear News, 10 Apr. 2026

The company recently snagged a $200 million government financing deal to aid its manufacturing expansion in Texas. —Brandon Lingle, Austin American Statesman, 10 Apr. 2026

FirstRand, which entered the UK in July 2006, was unusual in betting on the UK, whereas other South African lenders, such as Standard Bank and Absa, focused on expansion across Africa. —Tiisetso Motsoeneng, semafor.com, 10 Apr. 2026

Donors funded the $30 million expansion. —Brandee Gruener, Southern Living, 10 Apr. 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