underlie

verb

un·​der·​lie ˌən-dər-ˈlī 

underlay ˌən-dər-ˈlā  ; underlain ˌən-dər-ˈlān  ; underlying ˌən-dər-ˈlī-iŋ 

transitive verb

1

: to lie or be situated under

2

: to be at the basis of : form the foundation of : support

ideas underlying the revolution

3

: to exist as a claim or security superior and prior to (another)

4

archaic : to be subject or amenable to

Examples of underlie in a Sentence

A tile floor underlies the rug.

The river is underlain by limestone.

We discussed the principles that underlay their methods.

A theme of revenge underlies much of her writing.

Recent Examples on the Web

Named Robinhood Ventures Fund I, the vehicle is closed-end, meaning that people can buy and sell shares with each other, but not redeem them with Robinhood for the underlying assets. —Leo Schwartz, Fortune, 9 Mar. 2026

What emotions might be underlying these behaviors? —Staff Author, Parents, 9 Mar. 2026

What troubles many Americans today is not simply the possibility of conflict, but the sense that conclusions are being announced without the underlying proof being publicly tested. —Chicago Tribune, 8 Mar. 2026

Several independent legal experts told me that, legally, the Pentagon can likely get away with using OpenAI’s technology—versions of the models that underlie ChatGPT—for mass surveillance of Americans. —Matteo Wong, The Atlantic, 7 Mar. 2026

Word History

First Known Use

before the 12th century, in the meaning defined at sense 4

Rhymes for underlie

• apply
• awry
• belie
• bely
• bigeye
• bonsai
• buckeye
• comply
• coxae
• decry
• defy
• deny

Kids Definition

underlie

verb

un·​der·​lie ˌən-dər-ˈlī 

underlay -ˈlā  ; underlain -ˈlān  ; underlying -ˈlī-iŋ 

1

: to lie or be located under

2

: to form the foundation of : support

ideas underlying the revolt