唇亡齿寒的英文：
[Literal Meaning]
lip/loss/tooth/cold
If the lips are lost, the teeth will be cold.

[解释]
形容利害关系紧密相关。

[Explanation]
mutual dependent

[例子]
唇亡齿寒，如果我们的友军被打败了，敌人很快就会把我们包围的。

[Example]
Our ally and us are in the same boat: if they were defeated, we would soon be encircled by the enemy.

[英文等价词]
to be in the same boat

When the lips are gone the teeth will be exposed to the cold;be on intimate terms with each other
唇亡齿寒

Teeth are exposed when lips are gone,interdependence of neighboring states
唇亡齿寒