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 document also listed Type 2 diabetes as a secondary underlying cause. —Angel Saunders, PEOPLE, 25 Nov. 2025

To determine the fossils’ identity, Becker-Kerber and his colleagues analyzed the underlying chemical properties of lingering organic material within the fossils. —Taylor Mitchell Brown, Scientific American, 25 Nov. 2025

Another elderly person with underlying conditions died in January after a bird flu infection. —Katherine Dillinger, CNN Money, 22 Nov. 2025

The evident disparities provide insight into which policies and underlying structural issues may be behind the issues facing America’s growing group of senior citizens, as well as the strategies that have been—or could be—adopted to address these. —Hugh Cameron, MSNBC Newsweek, 21 Nov. 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