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

• abecedarian
• basal
• basic
• beginning
• elemental
• elementary
• essential
• fundamental
• introductory
• meat-and-potatoes
• rudimental
• rudimentary

Examples of underlying in a Sentence

the ocean and the underlying rock

the underlying differences between democracy and dictatorship

Recent Examples on the Web

This symptom can look slightly different for each person and vary based on the underlying cause. —Cristina Mutchler, Health, 18 Jan. 2025

The patient was over the age of 65 and had underlying medical conditions, according to health officials. —Youri Benadjaoud, ABC News, 17 Jan. 2025

Importantly, because many of these symptoms could be the result of another underlying condition, hypothyroidism is primarily identified through laboratory testing. —Caroline C. Boyle, USA TODAY, 17 Jan. 2025

This happens as a result of an underlying condition, typically an issue with your blood vessels or a disease that affects them, Dr. Rost says. —Sarah Klein, SELF, 16 Jan. 2025

Word History

First Known Use

1611, in the meaning defined at sense 1a

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