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.
The OpenAI deal is the cornerstone of Oracle’s pivot under executive chairman Larry Ellison from software to AI infrastructure services.
From Barron's • Jun. 9, 2026
When China's economy opened up in the 1980s, coal production surged, becoming the cornerstone of its industrial ambition.
From BBC • May 31, 2026
In addition, pumitamig, arguably the cornerstone of BioNTech’s oncology portfolio, is undergoing clinical trials to test its efficacy in patients with non-small cell lung cancer.
From Barron's • May 27, 2026
Brink would be a cornerstone player for almost any team in the league, yet she’s coming off the bench with high expectations for her to be one of the team’s most important players.
From Los Angeles Times • May 23, 2026
What if we then used that as a cornerstone for something bigger, a whole children’s health initiative that might help parents avoid some of the pitfalls I’d experienced?
From "Becoming" by Michelle Obama
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.
