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keystone

/ˈkiːstoʊn/  ·  say it: KEY·stohn

the central stone locking an arch together

In Architecture & Design

In more detail

1. (noun) the central stone at the top of an arch that holds all the other stones in place

2. (noun) the most important thing that something depends on; the basic principle or part that everything else is built on

Examples

• 1. The keystone of the arch was carved with decorative patterns.
• 2. Education is the keystone of a successful society.

How to use keystone

Keystone is used both literally in architecture and figuratively to describe something essential on which other things depend. The figurative sense is more common in modern English and emphasizes foundational importance rather than mere significance. It suggests that removing or compromising this element would cause the entire structure or system to fail.

Common phrases

• keystone species
• keystone habit
• keystone principle
• keystone of society
• keystone arch

Synonyms

cornerstone · foundation · linchpin · pillar · mainstay

Word family

keystones (plural)

A common mistake

Learners sometimes use 'keystone' when they mean merely 'important' rather than 'foundational or essential to the whole system'—keystone implies structural dependence, not just importance.

Nearby in Architecture & Design

girder, insulation, joist, lintel, loft, louver

Keep going

How to remember the words you read · Spaced repetition, explained