cornerstone

American  

[kawr-ner-stohn] / ˈkɔr nərˌstoʊn /

noun

1. a stone uniting two masonry walls at an intersection.

2. a stone representing the nominal starting place in the construction of a monumental building, usually carved with the date and laid with appropriate ceremonies.

3. something that is essential, indispensable, or basic.

   The cornerstone of democratic government is a free press.

4. the chief foundation on which something is constructed or developed.

   The cornerstone of his argument was that all people are created equal.

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cornerstone British  

/ ˈkɔːnəˌstəʊn /

noun

1. a stone at the corner of a wall, uniting two intersecting walls; quoin

2. a stone placed at the corner of a building during a ceremony to mark the start of construction

3. a person or thing of prime importance; basis

   the cornerstone of the whole argument

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Etymology

Origin of cornerstone

Middle English word dating back to 1250–1300; 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.

Example Sentences

“I wanted to honor the teams of curators who form the cornerstone of any institution’s vision through the exhibitions they bring to the public,” says Opie.

From Los Angeles Times • Apr. 15, 2026

Bread has long been a dietary cornerstone, sustaining societies for generations.

From Science Daily • Apr. 14, 2026

The consensus among scholars and practitioners in design is nearly unanimous: Usability is one of the cornerstone achievements of our society over the past century.

From Slate • Apr. 4, 2026

Speaking to reporters from Qatar, Healey said the Gulf nations had praised the contributions of UK forces describing them as "a cornerstone" to their defence.

From BBC • Mar. 31, 2026

She went on to read the Declaration of Sentiments, which was the cornerstone of the entire meeting.

From "Votes for Women!" by Winifred Conkling

Related Words

• essential
• foundation
• keystone
• linchpin
• mainstay
• pillar