The word 上面 is formed by combining two meaningful characters: 上, which carries the core idea of "up" or "above", and 面, which introduces the concept of a "surface", "side", or "face". Their combination is not merely additive but creates a new, integrated spatial concept. Visually and conceptually, 面 gives a dimensional, often horizontal, plane or area to the directional notion of 上, effectively forming the idea of "the top surface", "the area above", or "the upper side" of something.