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

• 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

Or anyone else who may be curious about not just the phenomenon of a modern-day dynasty but its underpinnings and the interwoven tales of the people behind it. —Kansas City Star, 8 Aug. 2025

Unparalleled integration with the Apple ecosystem, portability, and UNIX underpinnings. —PC Magazine, 1 Aug. 2025

Just no longer naively leaving these other crucial underpinnings like the environment, the economy and society to someone else to deal with. —Rob Day, Forbes.com, 26 July 2025

Replacement and reproduction parts are plentiful, and these cars’ simple mechanical underpinnings allow many enthusiasts to do their own wrenching. —Robert Ross, Robb Report, 5 July 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