The Chinese word 不禁 (bùjīn) is a compound formed through the grammatical combination of the negation adverb 不 (bù), meaning "not," and the verb 禁 (jīn), which in this context means "to restrain or contain (oneself)." Literally, the phrase translates to "cannot restrain (oneself)," but it functions as a fixed adverb meaning "involuntarily," "can't help but," or "spontaneously." It describes an action or emotion that emerges naturally and irresistibly, bypassing conscious control, such as laughing or sighing. Thus, its formation follows a standard verb-phrase structure that has become lexicalized as a single grammatical unit expressing a lack of restraint.