ex·​pan·​sion | \ ik-ˈspan(t)-shən How to pronounce expansion (audio) \

Definition of expansion

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
5a : 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

Keep scrolling for more

Other Words from expansion

expansional \ ik-​ˈspanch-​nəl How to pronounce expansional (audio) , -​ˈspan(t)-​shə-​nᵊl \ adjective

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.
See More

Recent Examples on the Web

The economic expansion this week became the longest in U.S. history, surpassing the 1990s boom, which lasted exactly a decade. Heather Long, Washington Post, "‘This doesn’t look like the best economy ever’: 40% of Americans say they still struggle to pay bills," 4 July 2019 The Hogan administration says RADA will invest nearly $4 million into the expansion. USA TODAY, "Kacey Musgraves, sneaker flap, skiing in July: News from around our 50 states," 3 July 2019 And the record for a lengthy U.S. economic expansion is set to be broken. Susan Tompor, Detroit Free Press, "How you can benefit from an unexpected shift in interest rates," 3 July 2019 But he was defeated June 4 by Candi CdeBaca, an outspoken progressive critical of major development projects, such as the I-70 expansion. Justin Wingerter, The Denver Post, "Construction company hires Denver Councilman Albus Brooks," 2 July 2019 To give the company an incentive to grow in the Nutmeg State, the town of Simsbury offered a tiered tax abatement on any future growth and a waiver of 50 percent of the permitting fees associated with the expansion. Emily Brindley, courant.com, "Ensign-Bickford plans Simsbury expansion with 140 new jobs," 2 July 2019 This buckling typically occurs at weak points in the concrete when the expansions push concrete against the joints and slabs where it is laid, according to CNN meteorologist Brandon Miller. Cnn.com Wire Service, The Mercury News, "It’s so hot in parts of Northern California that mussels are cooking in their shells," 2 July 2019 After three seasons hosting the expansion Tampa Bay Lightning, the Trop watched the NHL team leave for the Ice Palace, a new arena in downtown Tampa, in 1996. Joe Sheehan, SI.com, "Rays' Outrageous Montreal Plan Only Exists to Get New Stadiums Built—Again," 2 July 2019 Indeed, as the expansion entered its record-setting 121st month on Monday, signs of a new Gilded Age are all over. NBC News, "We're in the longest economic expansion ever — but it's the rich who are getting richer," 2 July 2019

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'expansion.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

See More

First Known Use of expansion

1611, in the meaning defined at sense 1

Keep scrolling for more

Learn More about expansion

Statistics for expansion

Last Updated

7 Jul 2019

Look-up Popularity

Time Traveler for expansion

The first known use of expansion was in 1611

See more words from the same year

Keep scrolling for more

More Definitions for expansion



English Language Learners Definition of expansion

: the act of becoming bigger or of making something bigger : the act of expanding
: a more complete and detailed written work or set of comments based on something shorter


ex·​pan·​sion | \ ik-ˈspan-shən How to pronounce expansion (audio) \

Kids Definition of expansion

: the act of growing or increasing : enlargement


ex·​pan·​sion | \ ik-ˈspan-chən How to pronounce expansion (audio) \

Medical Definition of expansion

1 : the act or process of expanding
2 : the quality or state of being expanded

Keep scrolling for more

Comments on expansion

What made you want to look up expansion? Please tell us where you read or heard it (including the quote, if possible).


providing supplementary assistance

Get Word of the Day daily email!

Test Your Vocabulary

Farm Idioms Quiz

  • cow coming home
  • What does 'poke' refer to in the expression 'pig in a poke'?
True or False

Test your knowledge - and maybe learn something along the way.

Word Winder's CrossWinder

Test Your Knowledge - and learn some interesting things along the way.

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!