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
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 state expansion also means protection for the rare riparian forest.
—
Kayla Moeller, CBS News, 23 June 2026
The University of Pittsburgh’s record-setting growth is reshaping both its campus and Oakland, as the university leans into a long-term expansion plan that adds student beds, new facilities and economic heft to one of Pennsylvania’s busiest urban districts.
—Gabby Sartori, USA Today, 23 June 2026
But in recent years, scientists have found that the expansion rate of the early universe and that of the more recent universe vary by approximately 9%.
—Quanta Magazine, 22 June 2026
Just in the last 12 years, the company has spent more than 50 million euros (approximately $57 million) on its textile business, including international expansion, updates to its sites in Brixen and Kufstein and investments in its laboratories.
—Sarah Jones, Footwear News, 22 June 2026
See All Example Sentences for expansion
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Opinions expressed in the examples do not represent those of Merriam-Webster or its editors.
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Kayla Moeller, CBS News, 23 June 2026
The University of Pittsburgh’s record-setting growth is reshaping both its campus and Oakland, as the university leans into a long-term expansion plan that adds student beds, new facilities and economic heft to one of Pennsylvania’s busiest urban districts.
—Gabby Sartori, USA Today, 23 June 2026
But in recent years, scientists have found that the expansion rate of the early universe and that of the more recent universe vary by approximately 9%.
—Quanta Magazine, 22 June 2026
Just in the last 12 years, the company has spent more than 50 million euros (approximately $57 million) on its textile business, including international expansion, updates to its sites in Brixen and Kufstein and investments in its laboratories.
—Sarah Jones, Footwear News, 22 June 2026
See All Example Sentences for expansion
Cite this Entry
“Expansion.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/expansion. Accessed 23 Jun. 2026.
Copy CitationKids 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
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