subjacent vs underlying

subjacent and underlying both are adjectives.

Word	Noun	Adjective	Verb	Adverb
subjacent	No	Yes	No	No
underlying	No	Yes	No	No

subjacent (adjective)	underlying (adjective)
lying nearby but lower	being or involving basic facts or principles
	in the nature of something though not readily apparent
	located beneath or below