Which prefix indicates a position 'above' or 'upon'?

The prefix that indicates a position 'above' or 'upon' is "epi-." This prefix is derived from Greek, where it commonly conveys the meaning of being on, upon, or over something. For example, in medical terminology, "epidermis" refers to the outer layer of skin, which is literally the layer above the dermis. Understanding this prefix is crucial in medical contexts, as it helps describe anatomical locations and relationships accurately, facilitating clear communication among healthcare professionals.