状语从句用法总结
下面是我整理的一些关于状语从句用法的总结， 希望能帮助大家更好地认识状语从句，提高英语水平。
一、由when, while, as引导的时间状语从句
1. when引导的时间状语从句中的谓语动词可以是延续性动词，也可以是瞬时动词。when有时表示“就在那时”。如：
When she came in, I was doing some housework. 瞬时动词
When I lived with the Smiths, we used to discuss international issues together. 延续性的动词
We were about to leave when he came in. when表示“就在那时”
2. while引导的时间状语从句中的谓语动词必须是延续性的，并强调主句和从句谓语动词所表示的动作同时发生或者相对应。如：
While my wife was reading the newspaper, I was watching TV.
was reading是延续性的动词，was reading和was watching同时发生
3. as 引导的时间状语从句中的谓语动词表示延续性的动作，一般用于主句和从句动作同时
发生，有时也可以强调动作一先一后发生。如：
We always sing as we walk.
As we were playing out, it began to snow.
二、由till或until引导的时间状语从句
till和until一般情况下两者可以互换，但是在强调句型中多用until。需要注意的是：如果主句中的谓语动词是瞬时动词时，必须用否定形式;如果主句中的谓语动词是延续性动词时，用肯定或否定形式都可以，但表达的意思不同。如：
Don’t open it till your birthday.
It was not until the meeting was over that he began to teach me English.
Continue in this direction until you see a sign.
I didn’t work until he came back.
三、由since引导的时间状语从句
1. 若since引导的状语从句的谓语动词是终止性的过去时，则从句表示的时间是“从动作开始的那一时刻起”。如：
He has studied very hard since he came to our school.
We have been missing them since they left here.
2. 若since引导的状语从句的谓语动词是持续性动词或表示状态的动词的过去式时，则从
句表示的时间是“从那持续动作或状态结束时算起”。如：
How long is it since you lived in Shanghai?
John is now with his parents in New York. It is already three years since he was a teacher.
四、由as soon as, immediately等引导的时间状语从句
as soon as, immediately, directly, instantly, the moment, the instant, the minute等这些词语均表示“一……就……”。如：
I want to see her the moment she arrives.
I came immediately I heard the news.
注意：hardly scarcely, rarely … when / before; no sooner … than也表示“刚……就……”，但是其主句使用过去完成时，从句用一般过去时，而且，当hardly, scarcely, rarely和no sooner位于句首时，主句应用倒装语序。如：
Hardly had we begun our walk when it began to rain.
I had no sooner left than she called.
五、由each time, every time引导的时间状语从句。如：
Each time she moved her head she let out a moan.
六、由by the time引导的时间状语从句
如果从句的谓语动词用一般过去式，主句的谓语动词用过去完成时;如果主句的谓动词用一般现在式，主句的谓语动词用将来完成式。如：
By the time they get here, we’ll have finished the work.
By the time you e here tomorrow, I will have finished this work.
七、由the first time引导的时间状语从句
the first time常引导时间状语从句，其重点不是讲第一次做什么，而是说明另一动作或情况;也可以作表语，强调到说话为止某一情况或动作的次数。如：
I knew we would be good friends the first time I met her.
比较：for the first time表示有生以来或一段时间内第一次做某事，在句中一般单独作状语。如：
The two girl students talked for the first time at the beginning of the term.
