cornerstone
Americannoun
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a stone uniting two masonry walls at an intersection.
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a stone representing the nominal starting place in the construction of a monumental building, usually carved with the date and laid with appropriate ceremonies.
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something that is essential, indispensable, or basic.
The cornerstone of democratic government is a free press.
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the chief foundation on which something is constructed or developed.
The cornerstone of his argument was that all people are created equal.
noun
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a stone at the corner of a wall, uniting two intersecting walls; quoin
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a stone placed at the corner of a building during a ceremony to mark the start of construction
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a person or thing of prime importance; basis
the cornerstone of the whole argument
Etymology
Origin of cornerstone
Middle English word dating back to 1250–1300; see origin at corner, stone
Explanation
A cornerstone is literally a stone at the corner of a building. It’s an important stone, so it also means “the basic part of something,” as in, the cornerstone of the suffragette movement was getting women the right to vote. When a building goes up, putting in the cornerstone is a big deal and people celebrate. Many cornerstones are engraved with historical information about the building, such as the year the building was built. The cornerstone is sometimes made of a different material from the rest of the building too. From the sense of "foundation," cornerstone also means "essential element.” If you’re really into Italian food, you might say that pasta is the cornerstone of your diet.
Vocabulary lists containing cornerstone
Determined to Stay
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The Secret Hum of a Daisy
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George's Cosmic Treasure Hunt
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Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
Another $2,000 is listed for Cornerstone Schools that year “to assist the inner city schools in Uganda,” which is what Cornerstone Schools does in Detroit and Cornerstone Development does not do in Uganda’s inner-city schools.
From Salon • Jun. 9, 2026
By 2005, the regular $2,000 Fellowship donation to Cornerstone Schools in Detroit was back.
From Salon • Jun. 9, 2026
Cornerstone has also brought on PJT Partners as its investment bank and Latham & Watkins as its legal counsel, the people said.
From The Wall Street Journal • Apr. 7, 2026
Birmingham 73, Colony 58: The Patriots advanced to the Division III state championship game against Cornerstone Christian after losing in the opening round of the City Section playoffs.
From Los Angeles Times • Mar. 11, 2026
The Bloods stood all along the back wall of Cornerstone Baptist.
From "The Boy in the Black Suit" by Jason Reynolds
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
