知识要点状语从句是副词性从句，它在句子中担任状语，修饰主句的动词、形容词或副词。根据修饰的方面，状语从句可以分为以下九种：时间状语从句、地点状语从句、原因状语从句、目的状语从句、结果状语从句、条件状语从句、方式状语从句、让步状语从句和比较状语从句。一、时间状语从句1.when指的是“某一具体的时间”。whenever指的是“在任何一个不具体的时间”。

When I came into the room, he was writing a letter.

当我进屋时，他正在写信。

We shall go there whenever we are free.

我们什么时间有空，我们就去那里。2.when意为“这时”或“在那个时候”，可以看作是并列句,这种用法的when分句一般位于句末。

I was walking along the street when suddenly someone patted me on the shoulder from behind.

我正在街上走着，这时忽然有人从后面拍我的肩膀。3.while指“在某一段时间里”，“在……期间”，while引导的动作必须是持续性的。

While it was raining, they went out.

天下雨的时候，他们出去了。

I stayed while he was away.

他不在的时候我在。4.as引导持续性动作，强调主句和从句的动作同时发生。

He hurried home, looking behind as he went.

他赶快回家，不时地一边走一边向后看。5.before译为在……之前

Be a pupil before you become a teacher.

先做学生，再做先生。6.after译为在……之后

He arrived after the game started.

比赛开始后，他到了。7.如主句动词是持续性动作，常用肯定式，表示“直到……为止”。从属连词为till/until

We waited till (until) he came back .

我们一直等到他回来。8.如主句动词是瞬间动词，常用否定式，表示“直……才”“在……以前不”，从句放在句首表示强调，一般用until

She didn’t stop working until eleven o’clock.

她到11点钟才停止工作。

Until he had passed out of sight, she stood there.

她站在那里看着，直到看不见他的身影。9.hardly…when和no sooner…than的意义相当于as soon as，但只表示过去发生的事情，主句为过去完成时，从句为过去时，如hardly或no sooner位于句首时语气强，而且主句的谓语要用部分倒装。

I had hardly got home when it began to rain.

我刚一到家，就下雨了。=Hardly had I got home when it began to rain.

No sooner had we got to the station than the train left.

我们刚到车站，火车就走了。

Hardly had we begun when we were told to stop.

我们刚开始就被叫停。10.在时间状语从句中，不能用将来时或过去将来时，而要用现在时或过去时代替将来时。

Every time I travelled by boat, I got seasick.

我每次乘船都晕船。

The moment I heard the song, I felt cheerful.

我一听到这首歌，就感到很愉快。

Next time you come, you’ll see him.

下次你来的时候，就会见到他。11.状语从句在主句之前时一般用逗号与主句分开，从句在主句之后则不必用标点符号。

Great changes have taken place in China since 1978.

自从1978年以来中国发生了巨大的变化。

As soon as I arrive in Shanghai, I’ll write to you.

我一到上海就给你写信。二、地点状语从句where与wherever意义基本相同，但后者语气较强，多用于书面语。

Where there is a will, there is a way.

有志者，事竟成。

Where there is water there is life.

哪里有水，哪里就有生命。

You are free to go wherever you like.

你可以随意到你喜欢的任何地方去。

Wherever you go, you must obey the law.

无论你去哪都要遵守法律。三、原因状语从句1.because用来回答why 的问题，语气最强一般放在主句之后

I came back late yesterday because I was on duty.

昨天我回来晚了，因为我值班。2.since表示既然或全已知的理由，稍加分析即可表明的原因，多放句首

Since everyone is here, let’s begin our meeting.

既然大家都到了，我们开始开会。3.as从句常放在句首，说明原因，主句说明结果，常用于口语中。

As he didn’t know much English, he looked up the word in the dictionary.

由于他英语懂得不多，他在字典中查阅这个单词。4.seeing (that), now that 和since, as 意义相似，他们都有“鉴于某个事实”的意思，that可以省去。

Now (that) the weather has cleared up,we can start our journey.

鉴于天气已经晴朗，我们可以启程了。

Seeing (that) he was badly ill, we sent for the doctor.

鉴于他病情严重，我们派人去请医生去了。四、目的状语从句

1.目的状语从句中常用情态动词may (might), can (could), should 等放在动词之前，从句往往放在主句之后，主从句之间不用任何标点符号，从属连词一般为that, so that, in order that, lest = for fear that。

I shall write down your telephone number that I may not forget.

我要把你的电话号码记下来，以免忘记。

We’ll tell you the truth so that you can judge for yourself.

我把真实情况告诉你，使你能自己作出判断。

They worked harder than usual in order that they could finish the work ahead of time .

他们比往常更加努力工作，为了能提前完成工作。

Put on more clothes lest (= for fear that ) you should catch cold.

多穿点衣服，以免患感冒。五、结果状语从句

1.so that前有逗号为结果状语从句。so…that的so后面跟形容词或副词。

We turned up the radio, so that everyone heard the news.

我们把收音机的音量放大，大家都听到了新闻。

He was so excited that he couldn’t say a word.

他十分激动，以致一句话都说不出来。2.such…that的such后面跟名词，如果名词是单数就要用such a /an…that还可以转换用so…that，语气较强

He gave such important reasons that he was excused.他说出了这么重要的理由，得到大家的谅解。

It is such an interesting novel that all of us want to read it.

It is so interesting a novel that all of us want to read it.

这是一本十分有意思的书，大家都想看。