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
Repositioning the visuals is further helped by autofocus, auto keystone correction, fit-to screen and resizing to avoid obstacles.
—New Atlas, 18 Apr. 2025
Mobilize Recovery is also partnering with keystone sponsors including Meta, iHeartMedia, Indivior, Braeburn, and SAMHSA’s Opioid Response Network, to enhance the reach and impact of the 2025 initiative.
—Jem Aswad, Variety, 15 Apr. 2025
That’s good news for farmers 20 minutes south of Sacramento in Clarksburg, where chenin blanc has been the keystone grape for decades.
—Benjy Egel, Sacbee.com, 3 Apr. 2025
The keystone of the arrangement was a 2016 U.S. commitment that Washington’s surveillance agencies would respect European privacy rights through a process overseen by an obscure U.S. body, the Privacy and Civil Liberties Oversight Board (PCLOB).
—Henry Farrell, Foreign Affairs, 3 Apr. 2025
See All Example Sentences for keystone
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New Atlas, 18 Apr. 2025
Mobilize Recovery is also partnering with keystone sponsors including Meta, iHeartMedia, Indivior, Braeburn, and SAMHSA’s Opioid Response Network, to enhance the reach and impact of the 2025 initiative.
—Jem Aswad, Variety, 15 Apr. 2025
That’s good news for farmers 20 minutes south of Sacramento in Clarksburg, where chenin blanc has been the keystone grape for decades.
—Benjy Egel, Sacbee.com, 3 Apr. 2025
The keystone of the arrangement was a 2016 U.S. commitment that Washington’s surveillance agencies would respect European privacy rights through a process overseen by an obscure U.S. body, the Privacy and Civil Liberties Oversight Board (PCLOB).
—Henry Farrell, Foreign Affairs, 3 Apr. 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 30 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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