Which anatomical term refers to lying face down?

The term that refers to lying face down is "prone." In anatomical terminology, "prone" specifically describes a position where the body is horizontal and facing downward. This term is often used in clinical contexts—for example, when discussing patient positioning for certain medical procedures or examinations.

The other terms relate to different positions: "supine" refers to lying face up; "upright" indicates a vertical position; and "recumbent" typically means lying down but does not specify the orientation of the body. Thus, when identifying the position of lying face down, "prone" is the accurate and appropriate term.