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 Netflix debut is part of a broader expansion push that spans consumer products, licensing and live experiences. — Naman Ramachandran, Variety, 24 Aug. 2026

The excavation was conducted between 2025 and 2026 ahead of an expansion of Pasta Garofalo's production facility, with the findings recently announced by the company in July. — Andrea Margolis, FOXNews.com, 23 Aug. 2026

While the robot horse remains more of a technological showcase than a practical replacement for conventional vehicles, its appearance at one of China’s largest robotics events also illustrates the rapid expansion of the country’s robotics industry. — Bojan Stojkovski, Interesting Engineering, 23 Aug. 2026

The contract, which comes amid a hiring push for the company, further cements the need for Electric Boat’s expansion, speakers said Friday. — P.r. Lockhart, Hartford Courant, 23 Aug. 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