初二英语if的用法

if从句和虚拟语气:

1. 当if后面接一般现在时的`动词时,表示对将来的一种推测. if sb do sth sb will/shall do sth. If you go with me, you shall be rewarded.

2. 当if后面接一般过去时的动词时,则是一种虚拟语气. if sb did sth sb would/should do sth. If I didnt make that mistake, I wouldt have suffered such a failure.

3. 当if后面接什么时态都可以时，if为“是否”的意思，句子为宾语从句. sb do sth if sb do sth. He said if rain was stop. 由if引导的条件状语从句，时态应该是主将从现，就是说主句用一般将来时，而从句用一般现在时表示将来。

例如 If it doesnt rain tomorrow, I will visit my former school. 这里从句就用一般现在时。当然if引导的从句也可以用虚拟语气，例如 If I got up early in the morning, I wouldnt miss the train.