keystone

noun

key·​stone ˈkē-ˌstōn 

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

3

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

• base
• basis
• bedrock
• bottom
• cornerstone
• footing
• foundation
• ground
• groundwork
• root
• underpinning
• warp
• warp and woof

Examples of keystone in a Sentence

Tourism is the city's economic keystone.

the keystone of his faith

Recent Examples on the Web

Autofocus and auto keystone correction should make setup relatively painless too. —New Atlas, 12 June 2025

The auto-focus and keystone correction simplify setup. —Shubham Yewale, PC Magazine, 10 June 2025

And while the fate of Trump’s tariffs — a keystone of his economic agenda — continues to play out in court, White House officials insist that the duties will remain, one way or another. —Josephine Rozzelle, CNBC, 30 May 2025

The wolves are native to Colorado, Rocky Mountain National Park, and the greater Rocky Mountain region, and wildlife management officials figured the keystone species would make its way back to the park on its own after the agency reintroduced them, McClatchy News reported. —Brooke Baitinger, Sacbee.com, 30 Apr. 2025

Word History

First Known Use

circa 1637, in the meaning defined at sense 1

Rhymes for keystone

• alone
• atone
• backbone
• bemoan
• bluestone
• breastbone
• brownstone
• capstone
• cheekbone
• condone
• curbstone
• cyclone

Kids 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