Below. This word is used when an organism is in anatomic position and it is necessary to describe a feature on its body so that others can understand without actually seeing the organism where something is in reference to something else. When talking about mammals, the foot is inferior to the knee.

Also see superior, anterior, posterior, ventral, dorsal, cephalic, caudal, proximal, distal, medial, lateral, superficial, deep, prone, supine, plane, and region.