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.