The word "请勿" is a formal and polite compound phrase used to express a prohibition, formed by combining the respectful verb "请" (qǐng), which means "to request" or "please," with the classical negative adverb "勿" (wù), meaning "do not." It functions as a fixed lexical unit, most commonly seen in public notices or written instructions (e.g., "请勿吸烟" – "Please do not smoke"), where "请" softens the command to convey courtesy, while "勿" delivers the unambiguous negative injunction, creating a tone that is both authoritative and respectful.