underpinning

noun

un·​der·​pin·​ning ˈən-dər-ˌpi-niŋ 

1

: the material and construction (such as a foundation) used for support of a structure

2

: something that serves as a foundation : basis, support

—often used in plural

the philosophical underpinnings of educational methods

3

: underwear

—usually used in plural

4

: a person's legs

—usually used in plural

Synonyms of underpinning

• basis
• foundation
• bedrock
• cornerstone

Examples of underpinning in a Sentence

the underpinnings of the theory have recently been called into question

the underpinnings of the bridge were seriously damaged in the collision

Recent Examples on the Web

George Borjas has provided the intellectual underpinnings of the White House’s sweeping immigration policy changes, including restrictions on H-1B visas. —Lauren Kaori Gurley, Washington Post, 7 Jan. 2026

Credit for its scientific underpinnings however, goes to Albert Einstein. —Katia Riddle, NPR, 31 Dec. 2025

But the lack of other specifics on the hardware and underpinnings suggests Benda is probably still working on it. —New Atlas, 29 Dec. 2025

There were no mathematical underpinnings to support my plays. —Eddie Brown, San Diego Union-Tribune, 20 Dec. 2025

Word History

First Known Use

15th century, in the meaning defined at sense 1

Rhymes for underpinning

• beginning
• binning
• dinning
• ginning
• grinning
• inning
• pinning
• sinning
• skinning
• spinning
• thinning
• tinning

Kids Definition

underpinning

noun

un·​der·​pin·​ning ˈən-dər-ˌpin-iŋ 

1

: the foundation used for support of a structure

2

: prop entry 1, support

3

: a person's legs

—usually used in plural