Puzzle #420 · July 26, 2026
key stone
Featured
Every day one two-word expression or compound word used in American English.
A keystone is the central, wedge-shaped stone at the peak of a masonry arch or vault. It is the final piece placed during construction, which locks all other stones into position and allows the structure to bear weight. -
Because of this crucial structural role, the term has several popular figurative and specialized meanings:
Figuratively: The most important or essential part of a system, plan, or idea upon which everything else depends. (e.g., “The right to free speech is the keystone of American democracy.”) dictionary.cambridge.org
Ecology: A keystone species is a plant or animal that plays a uniquely critical role in the way an ecosystem functions. Without it, the ecosystem would collapse or change drastically. - Lexicon Learning
Because of this crucial structural role, the term has several popular figurative and specialized meanings:
Figuratively: The most important or essential part of a system, plan, or idea upon which everything else depends. (e.g., “The right to free speech is the keystone of American democracy.”) dictionary.cambridge.org
Ecology: A keystone species is a plant or animal that plays a uniquely critical role in the way an ecosystem functions. Without it, the ecosystem would collapse or change drastically. - Lexicon Learning
Puzzle Appearances
The expression key stone has appeared in 1 puzzle:
- Puzzle #420 on July 26, 2026
Rate of Appearance in English Language Print
Google's Ngram project shows how often a pair of words has appeared in print every year since the 1800's.
Data from Google Books Ngram Viewer. Licensed under CC BY 3.0.
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