rudimentary vs underlying

rudimentary and underlying both are adjectives.

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

As adjectives, rudimentary and underlying are synonyms defined as:

rudimentary and underlying: being or involving basic facts or principles

Other synonyms of rudimentary include fundamental.

rudimentary (adjective)	underlying (adjective)
being or involving basic facts or principles	being or involving basic facts or principles
being in the earliest stages of development	in the nature of something though not readily apparent
not fully developed in mature animals	located beneath or below