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
This behavior is, of course, anathema to independent journalism, which is a keystone of democracy.
—Bill Goodykoontz, AZCentral.com, 2 July 2025
For me, a good spa is the keystone of a luxury hotel and The Spa at Estancia is a beauty.
—Lois Alter Mark, Forbes.com, 25 June 2025
For example, Panos Cosmatos created the films Beyond the Black Rainbow and Mandy, and Gaspar Noé’s Enter the Void was a keystone for us.
—Destiny Jackson, Deadline, 13 June 2025
The smiling panel out front is home to sensors that feed the system's autofocus, auto keystone correction, screen alignment and resize for obstacle avoidance chops for even more positioning ease and flexibility.
—Paul Ridden
june 27, New Atlas, 27 June 2025
See All Example Sentences for keystone
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Bill Goodykoontz, AZCentral.com, 2 July 2025
For me, a good spa is the keystone of a luxury hotel and The Spa at Estancia is a beauty.
—Lois Alter Mark, Forbes.com, 25 June 2025
For example, Panos Cosmatos created the films Beyond the Black Rainbow and Mandy, and Gaspar Noé’s Enter the Void was a keystone for us.
—Destiny Jackson, Deadline, 13 June 2025
The smiling panel out front is home to sensors that feed the system's autofocus, auto keystone correction, screen alignment and resize for obstacle avoidance chops for even more positioning ease and flexibility.
—Paul Ridden
june 27, New Atlas, 27 June 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 22 Jul. 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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