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
That has made Dover and Eaton , which have small portions of the data center as keystones of their stocks, considered washed up.
—Jim Cramer, CNBC, 13 Apr. 2025
The keystone of our fiscal strategy is economic growth.
—Wes Moore, Baltimore Sun, 12 Apr. 2025
As keystone species, parrotfish play a critical part in maintaining coral reef health by grazing on macroalgae that would otherwise suffocate coral—clearing space for reefs to regenerate.
—Ashlee Marie Preston, Forbes.com, 27 Mar. 2025
The projector comes with auto (vertical) keystone correction and corner fit, plus screen alignment courtesy of Digital Image Shrink and vertical image positioning without having to move the unit via Digital Shift.
—Paul Ridden, New Atlas, 15 Feb. 2025
See All Example Sentences for keystone
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Jim Cramer, CNBC, 13 Apr. 2025
The keystone of our fiscal strategy is economic growth.
—Wes Moore, Baltimore Sun, 12 Apr. 2025
As keystone species, parrotfish play a critical part in maintaining coral reef health by grazing on macroalgae that would otherwise suffocate coral—clearing space for reefs to regenerate.
—Ashlee Marie Preston, Forbes.com, 27 Mar. 2025
The projector comes with auto (vertical) keystone correction and corner fit, plus screen alignment courtesy of Digital Image Shrink and vertical image positioning without having to move the unit via Digital Shift.
—Paul Ridden, New Atlas, 15 Feb. 2025
See All Example Sentences for keystone
Cite this Entry
“Keystone.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/keystone. Accessed 23 Apr. 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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