【Prone】 ,  【supine】 ,  【prostrate】 ,  【recumbent】 ,  【couchant】 ,  【dormant】  are comparable when they mean lying upon a surface (as the ground or a floor).

【Prone】 implies a position with the face, chest, or abdomen lying on or turned toward the supporting surface.

【Supine】 applies to a position with the back against a supporting surface, the face upward, and may suggest lethargy, abjectness, or inertness.

【Prostrate】 basically applies to full-length proneness as in submission, fear, or helplessness; the term also may apply to a horizontal position either 【prone】 or 【supine】 that is typically brought about by a fall or weakness or shock.

【Recumbent】 may apply to lying down in any position of comfortable repose.

【Couchant】  and  【dormant】 , mainly technical heraldic terms in the senses here involved, apply to a 【prone】 body position, the former suggesting that the head is raised as if in watchfulness, the latter that it is lowered in sleep.