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
Just trying to get to the keystones in this instance.
—Lance Eliot, Forbes.com, 24 Jan. 2026
The action ties together seven independent local affiliates in the state, including one in Orlando, and is expected to be the keystone for additional units.
—Orlando Sentinel Staff, The Orlando Sentinel, 19 Jan. 2026
As a keystone in the AI boom, Nvidia has also been caught up in concerns that trillions of dollars are being poured into AI companies that are overhyped and overvalued, forming a bubble that will burst.
—Queenie Wong, Los Angeles Times, 9 Jan. 2026
To many in the US, the keystone of the American dream is a house.
—Michaëla De Lacaze Mohrmann, Artforum, 1 Jan. 2026
See All Example Sentences for keystone
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Lance Eliot, Forbes.com, 24 Jan. 2026
The action ties together seven independent local affiliates in the state, including one in Orlando, and is expected to be the keystone for additional units.
—Orlando Sentinel Staff, The Orlando Sentinel, 19 Jan. 2026
As a keystone in the AI boom, Nvidia has also been caught up in concerns that trillions of dollars are being poured into AI companies that are overhyped and overvalued, forming a bubble that will burst.
—Queenie Wong, Los Angeles Times, 9 Jan. 2026
To many in the US, the keystone of the American dream is a house.
—Michaëla De Lacaze Mohrmann, Artforum, 1 Jan. 2026
See All Example Sentences for keystone
Cite this Entry
“Keystone.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/keystone. Accessed 28 Jan. 2026.
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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