Final answer:
Prone is the term used to describe the position when the ventral surface of the body is facing down. Supine describes the opposite, a face-up orientation. Pronation is the action of turning the forearm so the palm faces backward, and supination is its opposite.
Step-by-step explanation:
The question pertains to anatomical terms that describe the position and movement of the body. When the front or ventral surface of the body is facing down, the position is referred to as prone. This term is specifically used to describe the orientation of the body and contrasts with the term supine, which describes a body that is lying face up. Within the context of the forearm and hand, it's important to differentiate between pronation, supination, flexion, and extension. Pronation of the forearm turns the hand to the palm backward position in which the radius crosses over the ulna to form an "X," while supination is the opposite, turning the hand to the palm forward position with the radius and ulna parallel.