条件状语从句，即满足某条件，动作才发生的句子。

条件状语从句的逻辑

最常见的条件状语引导词是if，还有unless, whether or not, in case (that), on condition that, provided, 还有隐含条件关系的but for，without等。

条件状语从句引导词

If

真实条件句，表现的是说话者的真正意图。

If you study harder, you will enter a good college. 如果你更努力得学习，你就能考入好大学。

If you love me, I will love you in turn. 如果你爱我，我将以爱回应你。

虚拟条件句，表示说话人的假设

If you were to give birth to a baby, I would die. 你敢生老二，我就敢死。

生二胎得寻求老大的理解

If he had arrived one minute later, she would have jumped. 如果他再晚来一分钟，她就可能跳下去了。

Unless

I will not speak with you unless you cut the ties with her. 除非你和她断交，我不会跟你说话。

Unless miracle happens, the factory will close. 除非发生奇迹，否则工厂得停业了。

On condition that

Chain reaction happens on condition that there is extremely high temperature and pressure. 只有在极端的高温高压的条件下，链式反应才会发生。

This will will be valid on condition that the applicant is dead, 在申请人死亡的条件下，本遗嘱才能生效。

Whether or not

She will not give you a glimpse whether you help her or not. 无论你帮不帮她，她都不会正眼瞧你。

They will not betray his master whether you threaten them with death or not. 无论你用不用死亡威胁他们，他们都不会背叛他们的主人。