状语从句在主从复合句中修饰主句中的动词、形容词或副词等，按意义可以分为时间、地点、原因、目的、结果、条件、方式、比较、让步等状语从句。
三.原因状语从句。
1.原因状语从句多由because, since, as 引导。because 引导的从句一般放在句末，表示直接的原因，语气最强，回答why提出的问题，重点在从句;since 引导的从句一般放在句首，表已知的原因，全句重在交代结果，比because 语气弱，常译作“既然”; as 引导的从句放在句首或句末，表示比较明显的原因，说明因果关系，语气较弱，重点在主句，译作“由于”。例如：
_____ you have seen both fighters,_____ will win ?(上海 95)
A.Since; do you think who B.As; who you think
C.When; whoever D.Since; who do you think
答案：D. since 表示“既然”，所传达的信息是显而易见的。再如：
As all the seats are full, he had to stand waiting.
---“Why aren’t you coming with us to the concert ?”
---“Because I have got a bad headache.”
此外，for 也可表示原因， 但它是并列连词，引出并列分句，表示间接原因，用来补充说明内容，或据此而作出某种推断。例如：
She must have wept, for there are tear trails on her cheeks.
2.now that也可引导原因状语从句，意思是“既然”，与since 同义，但更突出事实本身。
四.目的状语从句。
通常由so that, in order that, so, in case“以防、以免”等连词引导。例如：
He took the medicine on time so that he might get well again.
The teacher must speak clearly so that his students can/may understand well.
She has bought the book in order that she can follow the TV lessons.
1.目的状语从句中的谓语常含有may/might, can/could, should , will/would等情态动词，通常主句在前，从句在后，主句与从句之间没有逗号。
2.in order that 引导的目的状语从句和so that 引导的状语从句可以换用，但in order that多用于正式文体中， 而so 可用于口语或非正式文体中。例如：
We’ll sit nearer the front so (that) we can hear better.
3. in case 在非正式文体中,常引导目的状语从句，表示“以防、以免”等含义。例如：
He left early in case he should miss the train.
Take your raincoat in case it rains/ should rain.
五.结果状语从句。
通常由连词so that, so…that, such… that等引导。例如：
He had overslept, so that he was late for work.
He was so angry that he left the room without saying a word.
He made such an excellent speech that everyone admired him.
1.so…that和such…that 引导的结果状语从句都表示主句的动作或状态达到一定的程度而引起的结果。
so 是副词，用来修饰形容词、副词、分词或其它结构，such 是形容词，用来修饰名词或名词短语。例如：
There were so many people in the room that we couldn’t get in.
So badly was he injured that he had to go to the hospital. (so短语位于句首时，主句须倒装)
The book is so written that it gives a quite wrong idea of facts.
He told us such a funny story that we all laughed.
such修饰单数可数名词且名词前有形容词时，可用so替换such, 冠词与形容词交换位置，构成“so+ adj. +a(an) +名词”。上面的句子可以写成：
He told us so funny a story that we all laughed.
又如：This is such a beautiful chair that I’m thinking of buying it.
(= This is so beautiful a chair that I’m thinking of buying it.)
2.如何区别so that 引导的目的状语从句和结果状语从句?
(1).根据上下文及句子所表达的意思判断。
(2).根据句子的结构来判断。从句之前有逗号的常是结果状语从句;从句前有情态动词的多半是目的状语从句。例如：
She hurried , so that she caught the bus.(结果)
She hurried so that she might catch the bus.(目的)
I went to the lecture early, so that I got a good seat.(结果)
I’m going to the lecture early so that I may get a good seat.( 目的)
