狀語從句在主從復合句中修飾主句中的動詞、形容詞或副詞等，按意義可以分為時間、地點、原因、目的、結果、條件、方式、比較、讓步等狀語從句。
三.原因狀語從句。
1.原因狀語從句多由because, since, as 引導。because 引導的從句一般放在句末，表示直接的原因，語氣最強，回答why提出的問題，重點在從句;since 引導的從句一般放在句首，表已知的原因，全句重在交代結果，比because 語氣弱，常譯作“既然”; as 引導的從句放在句首或句末，表示比較明顯的原因，說明因果關系，語氣較弱，重點在主句，譯作“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”，所傳達的信息是顯而易見的。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， 但它是并列連詞，引出并列分句，表示間接原因，用來補充說明內容，或據此而作出某種推斷。例如：
She must have wept, for there are tear trails on her cheeks.
2.now that也可引導原因狀語從句，意思是“既然”，與since 同義，但更突出事實本身。
四.目的狀語從句。
通常由so that, in order that, so, in case“以防、以免”等連詞引導。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.目的狀語從句中的謂語常含有may/might, can/could, should , will/would等情態動詞，通常主句在前，從句在后，主句與從句之間沒有逗號。
2.in order that 引導的目的狀語從句和so that 引導的狀語從句可以換用，但in order that多用于正式文體中， 而so 可用于口語或非正式文體中。例如：
We’ll sit nearer the front so (that) we can hear better.
3. in case 在非正式文體中,常引導目的狀語從句，表示“以防、以免”等含義。例如：
He left early in case he should miss the train.
Take your raincoat in case it rains/ should rain.
五.結果狀語從句。
通常由連詞so that, so…that, such… that等引導。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 引導的結果狀語從句都表示主句的動作或狀態達到一定的程度而引起的結果。
so 是副詞，用來修飾形容詞、副詞、分詞或其它結構，such 是形容詞，用來修飾名詞或名詞短語。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短語位于句首時，主句須倒裝)
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修飾單數可數名詞且名詞前有形容詞時，可用so替換such, 冠詞與形容詞交換位置，構成“so+ adj. +a(an) +名詞”。上面的句子可以寫成：
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.如何區別so that 引導的目的狀語從句和結果狀語從句?
(1).根據上下文及句子所表達的意思判斷。
(2).根據句子的結構來判斷。從句之前有逗號的常是結果狀語從句;從句前有情態動詞的多半是目的狀語從句。例如：
She hurried , so that she caught the bus.(結果)
She hurried so that she might catch the bus.(目的)
I went to the lecture early, so that I got a good seat.(結果)
I’m going to the lecture early so that I may get a good seat.( 目的)
