Which position is defined as lying on the belly?

The term that describes lying on the belly is "prone." In medical terminology, "prone position" refers to a body orientation where a person lies flat with their face and torso down toward the ground. This position is often used in various medical examinations, treatments, or procedures, such as in physical therapy or when accessing certain areas of the body for diagnostic purposes.

The other terms listed have distinct meanings. "Supine" refers to lying on the back, which is the opposite of prone. "Distal" and "medial" are anatomical terms that describe locations on the body. "Distal" pertains to a point further away from the trunk or point of attachment, while "medial" refers to a position closer to the midline of the body. Understanding these terms is essential in the context of medical law and ethics, particularly when discussing patient positioning and care.