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

The underlying assumption is that having a nuclear umbrella is desirable and that nuclear deterrence theory is valid. —Siegfried Hecker, Foreign Affairs, 16 Dec. 2025

For a franchise as big as Demon Slayer, where the underlying intellectual property [created by Koyoharu Gotouge] has been loved and read by so many people, the first step for me was to make sure there was alignment in our interpretation of the source material. —Destiny Jackson, Deadline, 15 Dec. 2025

Daily habits can exacerbate underlying issues, too. —Daryl Austin, USA Today, 15 Dec. 2025

Even though the constitutional process was ultimately rejected by voters, this underlying discontent has not gone away. —Andra B. Chastain, The Conversation, 15 Dec. 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