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

The Royals started veteran infielder Adam Frazier at the keystone spot and recalled utilityman Nick Loftin from Triple-A Omaha. —Jaylon Thompson, Kansas City Star, 26 May 2024

That’s the keystone to a democracy, and democracy is the foundation of being part of government instead of a subject of it. —Dean Minnich, Baltimore Sun, 16 Mar. 2024

Word History

First Known Use

circa 1637, in the meaning defined at sense 1

Phrases Containing keystone

• keystone species

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