In medical terminology, what does "Epi-" refer to?

The prefix "epi-" in medical terminology means "above" or "upon." It is derived from Greek and is commonly used to indicate a position that is located on or above an anatomical structure. For instance, in the term "epidermis," it refers to the outermost layer of the skin, which lies above the dermis. This prefix can also imply a relationship to something that is external or superficial. Understanding this prefix is essential in medical contexts where it helps to accurately describe the location and relationships of structures within the body.