Subjacent
Part of speech: adjective
Definition: lying beneath or at a lower level; underlying
Underlying
Part of speech: adjective
Definition: lying underneathbasic or fundamentalimplicit
Example sentence: When I was born, I was effectively dead. Weird, I know. The doctors couldn't get any reaction from me, so I had to be brought round, and although it seemed like I was okay, there were underlying problems.