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

Known as keystone species, these creatures play a critical role in maintaining balance, diversity, and resilience. —Scott Hutcheson, Forbes, 7 Jan. 2025

The projector now features automatic screen alignment together with manual keystone correction, making setup relatively simple while also allowing for seamless switching between screen sizes. —Paul Ridden, New Atlas, 6 Jan. 2025

As a threatened species, gopher tortoises are called a keystone species because hundreds of other animals depend on them for their burrows. —Orlando Sentinel Staff, Orlando Sentinel, 3 Jan. 2025

The New York Yankees could be looking for an upgrade at the keystone. —Matt Robison, Newsweek, 20 Nov. 2024

Word History

First Known Use

circa 1637, in the meaning defined at sense 1

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