underlying

adjective

un·​der·​ly·​ing ˌən-dər-ˈlī-iŋ 

1

a

: lying beneath or below

the underlying rock is shale

b

: basic, fundamental

an investigation of the underlying issues

2

: evident only on close inspection : implicit

3

: anterior and prior in claim

underlying mortgage

4

: of or being present in deep structure

underlying word order

Synonyms of underlying

• basic
• rudimentary
• elementary
• fundamental
• introductory

Examples of underlying in a Sentence

the ocean and the underlying rock

the underlying differences between democracy and dictatorship

Recent Examples on the Web

China is also making rapid progress in open-source models—systems where the underlying model parameters and code are made publicly available—which Bengio warned could ultimately pose an even greater danger than powerful systems like Mythos. —Beatrice Nolan, Fortune, 17 Apr. 2026

Nazarian also discussed the importance of addressing the psychological component of plastic surgery, noting that no procedure will fix underlying unhappiness. —Melissa Rudy, FOXNews.com, 17 Apr. 2026

Too many programs have been built by translating legacy courses into a digital format while leaving the underlying instructional model intact. —Ian Gibson, Chicago Tribune, 16 Apr. 2026

While the recent rebound has helped lift major indexes toward all-time highs, underlying technical signals remain mixed. —Sean Conlon,lisa Kailai Han, CNBC, 16 Apr. 2026

Word History

First Known Use

1611, in the meaning defined at sense 1a

Rhymes for underlying

• applying
• belying
• complying
• decrying
• defying
• denying
• implying
• outlying
• relying
• replying
• stupefying
• supplying

Kids Definition

underlying

adjective

un·​der·​ly·​ing ˌən-dər-ˌlī-iŋ 

1

: lying under or below

the underlying rock

2

: fundamental entry 1 sense 1

Medical Definition

underlying

adjective

un·​der·​ly·​ing -ˌlī-iŋ 

: serving as a basis or cause (as of secondary symptoms)

the underlying brain malformation that caused the hydrocephalus

—R. M. Henig