The idiom "不合时宜" (bù hé shí yí) is formed through a classical Chinese syntactic structure where the negative adverb "不" (not) modifies the verb phrase "合时宜," which itself is a compact combination of the verb "合" (to suit, to conform) and the compound noun "时宜" (the needs or appropriateness of the time). Literally meaning "not conforming to the needs of the time," it functions as a fixed, metaphorical expression to describe something or someone as outdated, ill-timed, or out of sync with prevailing trends or circumstances.