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

• 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

However, if dairy is not the underlying cause of your acne, eliminating it from your diet likely won't improve your skin. —Merve Ceylan, Health, 12 Aug. 2025

Although the underlying internet protocols remained open and neutral, massive digital platforms at the application layer walled off participants from competing services by strategically breaking interoperability. —Christian Catalini, Forbes.com, 12 Aug. 2025

The treatments for tremors are directed towards the underlying medical cause. —Heidi Moawad, Verywell Health, 11 Aug. 2025

In May, leaders of the FDA published an article in the New England Journal of Medicine saying that, moving forward, the FDA would approve COVID-19 vaccines only for people ages 65 and older and younger people with underlying conditions. —Lisa Schencker, Chicago Tribune, 10 Aug. 2025

Word History

First Known Use

1611, in the meaning defined at sense 1a

Rhymes for underlying

• amplifying
• beautifying
• certifying
• clarifying
• classifying
• codifying
• crucifying
• edifying
• falsifying
• fortifying
• glorifying
• gratifying

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