key·​stone | \ ˈkē-ˌstōn How to pronounce keystone (audio) \

Definition of keystone

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

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Examples of keystone in a Sentence

Tourism is the city's economic keystone. the keystone of his faith

Recent Examples on the Web

Salmon are a keystone species in this region, critical as a food source for animals from bears to eagles to insects. Jim Robbins, New York Times, "How Long Before These Salmon Are Gone? ‘Maybe 20 Years’," 16 Sep. 2019 In short, transiting worlds have proved to be the keystones in the burgeoning search for Earth’s cosmic twins. Lee Billings, Scientific American, "Astronomers Find Water on an Exoplanet Twice the Size of Earth," 11 Sep. 2019 One national party official said the Alabama party made the keystone cops look organized. al, "Gov. Ivey admitted wearing blackface. The Alabama Democratic Party said nothing," 4 Sep. 2019 Because other species in the bay ecosystem depend on oysters performing their role, they are considered a keystone species. Julia Rentsch,, "Maryland oysters are having a bad year, and here’s why," 18 Aug. 2019 The friendship between Rick Dalton (Leonardo DiCaprio) and Cliff Booth (Brad Pitt) functions for Tarantino as both keystone and key. New York Times, "‘Once Upon a Time … in Hollywood’ Review: We Lost It at the Movies," 24 July 2019 The Red Sox, Rangers, Cubs, Padres and Rockies all fit the bill of teams that could use help at the keystone. Jon Tayler,, "The Best Possible Move for Every American League Team Before the Trade Deadline," 10 July 2019 In nature, rewilding is all about large-scale conservation that looks to restore natural cycles and habitats to protect keystone species. Pilar Guzmán, Condé Nast Traveler, "Editor's Letter: The Wisdom of the Wild," 10 Oct. 2018 Offshore wind is a keystone to the Northeast’s climate goals. Benjamin Storrow, Scientific American, "Major U.S. Offshore Wind Projects Still Face Hurdles," 22 July 2019

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'keystone.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of keystone

circa 1637, in the meaning defined at sense 1

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Statistics for keystone

Last Updated

18 Oct 2019

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Time Traveler for keystone

The first known use of keystone was circa 1637

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More Definitions for keystone



English Language Learners Definition of keystone

: a large stone at the top of an arch that locks the other stones in place
: something on which other things depend for support


key·​stone | \ ˈkē-ˌstōn How to pronounce keystone (audio) \

Kids Definition of keystone

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 for support

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More from Merriam-Webster on keystone

Rhyming Dictionary: Words that rhyme with keystone

Thesaurus: All synonyms and antonyms for keystone

Spanish Central: Translation of keystone

Nglish: Translation of keystone for Spanish Speakers Encyclopedia article about keystone

Comments on keystone

What made you want to look up keystone? Please tell us where you read or heard it (including the quote, if possible).


a topic to which one constantly reverts

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