audible
capable of being heard; loud enough to be heard
inaudible
incapable of being heard; not audible
comprehensible
capable of being comprehended (understood);
understandable; intelligible
incomprehensible
not understandable; unintelligible
feasible
capable of being done or accomplished; possible; practicible; workable
unfeasible
not feasible; impracticable; unworkable
tangible
capable of being touched or felt by touching; palpable; real; actual
intangible
incapable of being touched; not tangible; impalpable
visible
capable of being seen; perceptible; evident
invisible
incapable of being seen; not visible; imperceptible