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

Keep scrolling for more

Examples of keystone in a Sentence

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

Recent Examples on the Web

Meanwhile, Jimmie is forced to confront the keystone of his family mythology: the house wasn’t in fact built by his grandfather. Richard Brody, The New Yorker, "Review: The Disappointing Blandness of “The Last Black Man in San Francisco”," 5 June 2019 As the heir of both the House of Tudor and the House of York, Arthur was a keystone in Henry VII's plan to prevent rival factions from rising against his claim to the throne and maintaining peace in the kingdom. Lauren Hubbard, Town & Country, "The Cause of Prince Arthur Tudor's Death Remains a Medical Mystery," 13 May 2019 Overmastering imitation, more than parody, is a keystone of his criticism. Zachary Fine, WSJ, "‘Attention’ Review: Anatomist of Our Disorder," 30 Aug. 2018 Tax cuts, deregulation, the keystone pipeline is being built. Fox News, "Ronna McDaniel: Trump is an asset on the campaign trail," 11 Aug. 2018 In scientific lingo, penguins aren’t a keystone species—one on which other creatures depend for survival. Jo Craven Mcginty, WSJ, "Counting Penguins Isn’t Always Black and White," 2 Nov. 2018 Members are known as Mormons because of the religion’s keystone scripture, the Book of Mormon. Brady Mccombs, USA TODAY, "Thomas S. Monson, president of Mormon church, dies at 90," 3 Jan. 2018 The North Atlantic Treaty Organization, which has been a keystone of global security since its formation in 1949, does not involve a membership that collects dues. W.j. Hennigan, Time, "President Trump Says NATO Allies Owe the U.S. Money. He's Wrong," 11 July 2018 Dodd-Frank was the keystone of Obama’s post-2008 recession measures to prevent another meltdown., "Trump’s trophy case," 15 June 2018

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.

See More

First Known Use of keystone

circa 1637, in the meaning defined at sense 1

Keep scrolling for more

Learn More about keystone

Statistics for keystone

Last Updated

14 Jun 2019

Look-up Popularity

Time Traveler for keystone

The first known use of keystone was circa 1637

See more words from the same year

Keep scrolling for more

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

Keep scrolling for more

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 device or gadget

Get Word of the Day daily email!

Test Your Vocabulary

Words for Summer: A Quiz

  • a closeup of a sunflower
  • Which of the following words means “of or relating to summer”?
Spell It

Can you spell these 10 commonly misspelled words?

Word Winder's CrossWinder

Test Your Knowledge - and learn some interesting things along the way.

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!