The word 恰当 is formed by combining two independent characters, each contributing a layer of meaning to create a unified concept. The first character, 恰, carries the inherent sense of exactness, precision, or just rightness. The second, 当, conveys the idea of being proper, fitting, or appropriate to the circumstance. Their fusion is not merely additive but synergistic, where 恰 intensifies the precision of the suitability denoted by 当, resulting in the complete meaning of "apt", "precisely suitable", or "fitting perfectly". It is a standard formation in Chinese where two complementary meaning-based units (morphemes) merge to express a single, more specific idea.