条件状语从句 

主要连词：if, unless（除非=if...not...）, as long as（只要）等。

【注意】条件状语从句要符合“主将从现”的原则：即主句用一般将来时，从句用一般现在时。例如： 

If it is fine tomorrow，we will have a picnic outdoors.

如果明天天气好，我们会在户外野餐。

Unless you work hard, you won't succeed.（=If you don't work hard, you won't succeed.）

除非你努力工作，否则你不会取得成功。

As long as you go, I will go.

只要你去，我就会去。