The Chinese word "不当" (bùdàng), meaning "inappropriate" or "improper," is a compound formed through the morphological process of combination, where two independent characters merge to create a new, fixed meaning. The first character, "不" (bù), is a common negating adverb meaning "not." The second character, "当" (dāng), is a versatile verb or adjective carrying core meanings of "to be," "to serve as," or "fitting/appropriate." When combined, the structure follows a typical [adverb + adjective/verb] pattern where "不" directly negates the quality of "当," semantically fusing to convey the specific concept of "not fitting" or "not suitable." This fusion has become lexicalized over time, evolving from a literal phrase in classical texts into a standard modern word used as both an adjective and, in certain grammatical contexts, a verb.