时间状语从句(1)常用的连词有when,while,before,after,until(till),since,as soon as等.
(2)时间状语从句中一般不用将来时,若谈论将来的事情,往往用一般现在时代替,
如：I’ll go on with the work when I come back tomorrow./As soon as he finishes
the work,he will come to see me.
(3)when和while都表示“当……的时候”,但有区别.
when强调“特定时间”,如：
There was a loud knock at the door when he was just falling asleep.
while表示的时间是一段,而不是一点,如：
While he was having supper,he heard someone knock at the door.
while有时还有对比的含义,如：
While I was reading,he was writing.
2.原因状语从句(1)常由because,since,as引导.
(2)because表示直接的原因,着重点在从句,用于回答why,语气最强.
I can’t go to school because I am ill.
since一般表示对方已知的,无须加以说明的既成事实的理由,全句中心在主句,语气比because弱,常译为“既然”,如：Since you are ill,I’ll go alone.
as表示十分明显的原因,一般说明因果关系,着重点在主句,语气较弱.常译为“由于”,如：As it is raining hard,we won’t go hiking.
for是个并列连词,只能放在另一个并列分句后面,表示一种推理或解释,或用作附加说明,而不是指理由或原因,语气最弱,一般不放在句首,常译成“因为”,如：You haven’t met him,for he didn’t come here.
3.条件状语从句
常由if(假如、如果)No matter(不管)来引导,如：No matter what he says,I won’t believe him,如果主句是一般将来时,从句往往用一般现在时来表示将来,如：I’ll go for a picnic if it is fine.
4.结果状语从句
一般由so...that,such...that引导,如：It’s such a heavy box that nobody can move it.
The box is so heavy that nobody can move it.
