keystone

Word Parts

key + stone

Pronunciation

• IPA ^(key): /ˈkiːstoʊn/
• Hyphenation: key‧stone

Noun

Singular keystone

Plural keystones

A keystone.

1. (countable) A keystone is the most important part of something, on which everything else depends.

   Trust is the keystone of any strong relationship.

2. (usually before a noun) A keystone part is the most important or foundational part of a system or plan.

   Education is the keystone policy of the new government.

   Keystone species play a critical role in maintaining the structure of an ecosystem.

3. (countable) A keystone is the central stone at the top of an arch that holds the other stones in place.

   The old bridge's arch was held up by a single keystone.

Related words

• key
• stone