The idiom **千载难逢 (qiān zǎi nán féng)** is formed through a logical, parallel structure where "千载" (a thousand years, representing an extremely long period) modifies and intensifies "难逢" (hard to meet or encounter). Literally meaning "an opportunity that is hard to come by even in a thousand years," it functions as a hyperbolic metaphor to emphasize the extreme rarity and preciousness of a situation or chance. The formation follows a common pattern in classical Chinese where a time span ("千载") is combined with a descriptive phrase ("难逢") to create a vivid, figurative expression denoting a once-in-a-lifetime event.