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Definition of keystone

keystone

/ˈkiː.stoʊn/
key · stone

Plural:keystones
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keystone Lexical Profile

keystone Game Scores & Validity

• noun

1

The fundamental principle, element, or core component on which an entire system, policy, or process depends.

Example

"Freedom of speech remains the absolute keystone of any functioning democratic society."


2

A biological species or ecological entity that exerts a disproportionately large impact on its surrounding environment, crucial for maintaining the structure of an ecological community.

Example

"As an apex predator, the sea otter acts as a keystone by keeping the sea urchin population in check and protecting the kelp forests."


3

The central, wedge-shaped stone at the apex of a masonry arch or vault that locks all the other stones into position.

Example

"The master mason carefully lowered the keystone into place, ensuring the magnificent stone arch could finally support its own weight."

Synonyms
View all synonyms for keystone

• Rhymes for keystone

Word Origin & Etymology

First recorded in the mid-1600s as a literal translation of the Italian 'chiave' or Latin 'clavis', formed by compounding 'key' and 'stone' to describe the central stone that locks a masonry arch.

Cite this Entry


Wordmom. (2026). Definition of Keystone. In Wordmom Dictionary. Retrieved Oct 12, 2026, from https://wordmom.com/dictionary/keystone
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