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

The fingernail-sized device uses a network of light-processing components and an optimisation algorithm to identify and physically separate the underlying coherence modes within a mixed optical field. — Neetika Walter, Interesting Engineering, 4 Nov. 2026

Having patched the underlying bootloader vulnerability in 2022, Microsoft’s May 2023 patch batch included security updates to prevent attackers from loading older vulnerable boot managers. — Dan Goodin, ArsTechnica, 3 Nov. 2026

The underlying signal processing draws on foundational research from the INSIDE Institute for NeuroAI, translating complex non-invasive BCI (brain-computer interface) concepts into a practical, gel-free form factor for daily life. — New Atlas, 3 Nov. 2026

The individual, who had underlying medical conditions, was hospitalized with severe illness after contracting avian influenza through exposure to infected livestock at a local dairy facility. — Khloe Quill, FOXNews.com, 3 Nov. 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