1
: the wedge-shaped piece at the crown of an arch that locks the other pieces in place see arch illustration
2
: something on which associated things depend for support
determination, a keystone of the puritan ethic—
L. S. Lewis
L. S. Lewis3
or keystone species
: a species of plant or animal that produces a major impact (as by predation) on its ecosystem and is considered essential to maintaining optimum ecosystem function or structure
Examples of keystone in a Sentence
Tourism is the city's economic keystone.
the keystone of his faith
Recent Examples on the Web
Open Pine Forests Eufala National Wildlife Refuge One of the most significant environments for wintering rusty blackbirds, Eufala National Wildlife Refuge is also host to an ecosystem of wiregrass and longleaf pines, a keystone tree species native to the Southeastern United States.
—Catherine Jessee, Southern Living, 8 Mar. 2025
The previous Trump administration also attempted to undo protection for the sage grouse keystone species, largely enabling oil and gas interests that had long opposed the extent of the grouse conservation efforts.
—May Wang, JSTOR Daily, 6 Mar. 2025
As Germany prepares to celebrate 70 years in the military alliance in May, Merz questioned Washington’s future as its keystone member.
—Alexander Smith, NBC News, 22 Feb. 2025
Chicago soul giant Jerry Butler, who succeeded early hits as lead singer of the keystone R&B group Impressions and a notable solo career with years as a Windy City politician, has died, according to the Chicago Sun TImes.
—Chris Morris, Variety, 21 Feb. 2025
See All Example Sentences for keystone
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Catherine Jessee, Southern Living, 8 Mar. 2025
The previous Trump administration also attempted to undo protection for the sage grouse keystone species, largely enabling oil and gas interests that had long opposed the extent of the grouse conservation efforts.
—May Wang, JSTOR Daily, 6 Mar. 2025
As Germany prepares to celebrate 70 years in the military alliance in May, Merz questioned Washington’s future as its keystone member.
—Alexander Smith, NBC News, 22 Feb. 2025
Chicago soul giant Jerry Butler, who succeeded early hits as lead singer of the keystone R&B group Impressions and a notable solo career with years as a Windy City politician, has died, according to the Chicago Sun TImes.
—Chris Morris, Variety, 21 Feb. 2025
See All Example Sentences for keystone
Articles Related to keystone
Cite this Entry
“Keystone.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/keystone. Accessed 12 Mar. 2025.
Copy CitationKids Definition
keystone
noun
key·stone
ˈkē-ˌstōn 
1
: the wedge-shaped piece at the top of an arch that locks the other pieces in place
2
: something on which other things depend
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