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

Across three conversations with leaders working in human rights, social innovation, and critical infrastructure, the underlying premise was clear. —Monica Sanders, Forbes.com, 25 Jan. 2026

The underlying allegations of this investigation are particularly fraught with danger for the state police and its leadership. —Kevin Rennie, Hartford Courant, 24 Jan. 2026

Yet this also means that the operation and underlying principles of its onboard equipment are very sophisticated, according to Global Times. —Prabhat Ranjan Mishra, Interesting Engineering, 23 Jan. 2026

When Sleep May Signal an Issue While occasional sleep changes are normal, too much or too little sleep can sometimes point to an underlying problem. —Hannah Silverman, Parents, 23 Jan. 2026

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