Chinese idiom · 成语
唇亡齿寒
Meaning
Mutual dependence; one’s loss affects another.
Character by character
Origin and story
Historical accountIn the Zuo Zhuan (左傳), under the fifth year of Duke Xi, Jin asks to send troops through Yu to attack Guo. The adviser Gong Zhiqi warns Yu’s ruler that Guo is its protective neighbor: if Guo falls, Yu will follow. He invokes the existing proverb that when the lips are gone, the teeth become cold.
Yu’s ruler rejects the warning and grants passage. The account relates that Jin destroys Guo and then takes Yu as well. The idiom thus expresses shared vulnerability, not merely affection or friendly relations. It is especially apt when losing a neighbor, partner, or protective support exposes the other party to danger.
Sources and further reading
In everyday life
镇上的工厂和运输公司唇亡齿寒，工厂一停产，运输公司的订单也会大减。
The town’s factory and transport company depend on each other; if production stops, the transport company’s orders will fall sharply too.
Emphasizes how harm to one party threatens the other, rather than closeness alone.