underlying

(verb) be or form the base for. Synonyms: underlie.

(verb) lie underneath. Synonyms: underlie.

(adj) in the nature of something though not readily apparent. Synonyms: implicit in(predicate), inherent. Examples: "Shortcomings inherent in our approach." "An underlying meaning."

(adj) located beneath or below.

(adj) being or involving basic facts or principles. Synonyms: fundamental, rudimentary. Examples: "The fundamental laws of the universe." "A fundamental incomatibility between them." "These rudimentary truths." "Underlying principles."