The word 适当 is formed by combining two independent characters, each contributing its core conceptual meaning to create a new, composite idea. The first character, 适 (shì), carries the inherent notion of "to fit" or "to suit", implying alignment or compatibility. The second, 当 (dāng), contributes its essential meaning of "to be proper", "to serve as", or "to bear". When joined, the concept flows from "fitting" a condition (适) directly into the state of "being proper" or "adequate" for it (当), thereby synthesizing the holistic idea of something being "appropriate", "suitable", or "just right" because it correctly matches and meets the requirements of a given situation.