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
Synonyms
Examples of keystone in a Sentence
Tourism is the city's economic keystone.
the keystone of his faith
Recent Examples on the Web
But before long there were also scientific references to keystone herbivores, keystone plants, keystone pollinators, even keystone pathogens.
—Lesley Evans Ogden, Smithsonian Magazine, 9 May 2024
The compact projector adjusts the image for your picture with automatic leveling, focus, and keystone technology.
—Carrie Honaker, Southern Living, 18 Oct. 2023
See all Example Sentences for keystone 
Lesley Evans Ogden, Smithsonian Magazine, 9 May 2024
The compact projector adjusts the image for your picture with automatic leveling, focus, and keystone technology.
—Carrie Honaker, Southern Living, 18 Oct. 2023
See all Example Sentences for keystone
These examples are programmatically compiled from various online sources to illustrate current usage of the word 'keystone.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.
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Cite this Entry
“Keystone.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/keystone. Accessed 29 May. 2024.
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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