Verb

To lie in a position directly beneath.

A stratum of clay underlies the surface gravel.

To lie under or beneath.

To serve as a basis of; form the foundation of.

a doctrine underlying a theory

*{{quote-magazine, year=2013, month=July-August, author= Sarah Glaz

, title= Ode to Prime Numbers , volume=101, issue=4, magazine=(American Scientist) , passage=Some poems, echoing the purpose of early poetic treatises on scientific principles, attempt to elucidate the mathematical concepts that underlie prime numbers. Others play with primes’ cultural associations. Still others derive their structure from mathematical patterns involving primes.}}

To be subject to; be liable to answer, as a charge or challenge.

* Sir Walter Scott

The knight of Ivanhoe underlies the challenge of Brian der Bois Guilbert.

(mining) To underlay.

Verb

(obsolete) To go or move under or beneath.

To experience; to pass through a phase.

* {{quote-magazine, date=2013-01-01

, author=Paul Bartel, Ashli Moore , title=Avian Migration: The Ultimate Red-Eye Flight , volume=101, issue=1, page=47–48 , magazine= citation , passage=Many of these classic methods are still used, with some modern improvements. For example, with the aid of special microphones and automated sound detection software, ornithologists recently reported […] that pine siskins (Spinus pinus ) undergo an irregular, nomadic type of nocturnal migration.}}

The project is undergoing great changes.

To suffer or endure; bear with.

The victim underwent great trauma.

She had to undergo surgery because of her broken leg.