WordNet sense 1 (lying nearby but lower):

subjacent

WordNet sense 2 (being or involving basic facts or principles):

fundamental, rudimentary

WordNet sense 3 (pertaining to or constituting a base or basis):

basic

WordNet sense 4 (in the nature of something though not readily apparent):

inherent, implicit in

WordNet sense 5 (implied though not directly expressed; inherent in the nature of something):

implicit, inexplicit