在复合句中作状语的从句，叫做状语从句（the Adverbial Clause）.
when引出的时间状语从句，其中的动词既可以是延续性动作的动词，也可以是瞬间性动作的动词，而且可以表示主语的动作和从句的动作同时发生，或者从句的动作发生在主句的动作之前。
e.g.
When you apply for a job, you must present your credentials.
When the students heard the teacher's footsteps, they all stopped talking.
when还可以表示just then(正在那时，突然)的意思，此时其所引导的从句只放在主句之后。
e.g.
We were about to start when it began to rain.
as引出的时间状语从句，其动作是延续性的，而且侧重表示主句和从句的动作同时发生.
e.g.
As the students walked to their dormitories,they sang happily.
while表示"在某一段时间里"或"在...期间"，其所引出的从句的动作是延续性的，且侧重表示主句和从句的动作同时发生。
e.g.
While the teacher paraphrased the text in English,the students listened attentively and took notes.
while还可用作并列连词，相当于whereas，连接一个表示对比的并列分句。
e.g.
Mary was dressed in blue while Jane was dressed in red.
whenever,every time,each time任何时候;每当
e.g.
Whenever I met her,she was studying.
Every time I met her,she was staying with him.
Each time I met her,she was listening to the music.
since(自从，从...以来),ever since(从那时起一直到现在;此后一直)
since,ever since引导的从句通常用一般过去时，主句中的谓语动词通常用完成时.
e.g.
We've never met since we graduated from the college.
It is six years since we parted.
before(在...之前),after(在...之后)
before引导的从句一般表示主句的动作发生在从句动作之前，如从句是过去时,主句一般用过去完成时.
e.g.
I had written my dissertation before my supervisor went abroad.
after引导的从句，表示主句的动作发生在从句动作之后，如主句是过去时,从句一般用过去完成时.
e.g.
After the boy had finished his homework,he played football with his friends.
till,until
until比较正式，可用于句首，而till一般不用于句首.till和until所表示的意义相同，但要注意以下情况:
如主句的谓语动词是延续性动词，就常用肯定式表示"直到...为止"
e.g.
He will remain in college until(till) he finishes his Ph.D course.
如主句的谓语动词是非延续性动词，就常用否定式表示"直到...才"或"在...之前（不）".此时的till和still可用before替换，意义差别不大。
e.g.
I won't go with you until(till) I finish my homework.
as soon as,immediately,directly,once,the minute/moment (that) etc.
as soon as,immediately,directly,once,the minute/moment (that)等引导的从句都表示从句的动作一发生，主句的动作随即就发生，常译为"一...就...".
e.g.
As soon as we got home,the telephone rang.
I recognized her immediately I saw her.
Directly the teacher came in everyone was quiet.
Once you understand this rule,you'll have no further difficulty.
I want to see her the minute/moment (that) she arrives.
no sooner...than,hardly(scarcely)...when
no sooner...than,hardly(scarcely)...when引导的从句也表示"一...就","刚...就"的含义。但它们只用于过去时:主句中的动词一般用过去完成时，从句用过去时.no sooner,hardly位于句首时，主句的谓语要部分倒装.
e.g.
He had no sooner arrived home than he was asked to start on another journey.
No sooner had he arrived home than he was asked to start on another journey.
No sooner had the words been spoken than he realized that he should have remained silent.
Hardly had he reached the airport when the plane took off.
地点状语从句
引导地点状语从句的连词有:where(在..地方),wherever(无论哪里，在任何地方),everywhere(每一...地方，到处),anywhere（任何地方）.where总是放在主句后，绝不提前。
e.g.
Where there is a will,there is a way.
You can go wherever(anywhere) you like these days.
Wherever (Everywhere) they went,they were warmly welcomed.
I'll take you anywhere you like.
原因状语从句
引导原因状语从句的连词有:because,as,since,for,now that,seeing that,considering (that),in that等。
e.g.
I didn't go abroad with her because I couldn't afford it.
Since traveling by air is much faster, they decided to take a plane.
As it is snowing, we shall not climb the mountain.
It must have rained last night, for the ground is wet.
Now (that) you've passed your test, you can drive on your own.
Seeing (that) the weather is bad, we'll stay at home.
Considering (that) he's only been learning English a year, he speaks it very well.
Advertisement is distinguished from other forms of communication in that the advertiser pays for the message to be delivered.
I'm in a slightly awkward position, in that he's not arriving until 10th.
条件状语从句
引导条件状语从句的连词或词组:if（如果）,unless（除非）,as(so) long as（只要）,on condition that(条件是...),provided/providing that（假如）,suppose/supposing（假如）,in case（如果）,for fear(that/lest)(惟恐;以免),only if(只要;只有),if only(但愿;要是...该多好)等。如果主句是将来时，条件状语从句用一般现在时表示。
unless的意义相当于"if...not"，而且语气较强，一般不用于虚拟语气.
e.g.
I'll buy a computer if I am able to save up enough money.
Unless the weather was bad,my father always used to take a walk in the evening.
suppose/supposing that,provided/providing (that)假如
e.g.
Suppose you had a million pounds -- how would you spend it?
Supposing (that) it rains,can we play the match indoors?
I will agree to go provided/providing (that) my expenses are paid.
as(so) long as,on condition that,in case
as(so) long as(只要...就...),on condition that(在...条件下;倘若),in case(以防万一，万一，如果).
e.g.
As long as you love me.
As long as it doesn't rain,we can play.
You can go out on condition that you wear an overcoat.
You'd better take an umbrella in case it rains.
only if ,if only
only if引导真实条件句，用于句首，主语谓语倒装.
e.g.
Only if a teacher has given permission,is a student allowed to enter this room
if only一般引导虚拟条件状语从句或感叹句.
用一般过去式或would/could do表与现在或未来事实相反的愿望；用过去完成时表与过去事实相反的愿望，意为‘但愿’.
e.g.
If only he had come,he would have met you.
If only I could swim.
让步状语从句
让步状语从句的连词或词组有:although虽然，though虽然，even if/though即使;纵然;尽管，as尽管，while尽管，whoever(no matter who)不管谁，whatever(no matter what)无论什么，whenever(no matter when)无论什么时候，wherever(no matter where)无论哪里，however(no matter how)无论怎样，whether..or不论...还是。
e.g.
Although they have been talking for a long time,he cannot make her believe him.
Though they lack offcial support,they continue their struggle.
Though he is old,yet(still,nevertheless) he works day and night.
Even if I failed again,I will not give up the experiment.
I like her even though she can be annoying.
whatever(whoever,whichever,whenever...)/no matter what(who,which,when...)
e.g.
Whoever(No matter who) wants to speek to me on the phone,tell them I'm busy.
Wherever(No matter where) you go,I'm right here waiting for you.
Whenever(No matter when) you call on us,you are welcome.
as虽然;尽管
as引导让步状语从句时，常放在作表语，状语或谓语的一部分的形容词，名词，副词或动词原形之后。如果是单数名词或形容词的最高级作表语，不再用冠词。
e.g.
Strong as you may be,you cannot lift it.
Late as it was,they continued to study.
Youngest as he is in our class,he studies very well.
Child as she is,She knows a lot.
Hard as he tried,he was unable to make much progress.
Much as I like you,I couldn't live with you.
Much as I would like to stay,I really must go home.
Call as you may,he will not come.
Published as it was such a time,his work attracted much attention.
whether..or 不管;无论
e.g.
Whether it rains or not, we're playing football on Sunday.
Whether she is sick or well, she is always cheerful.
目的状语从句
引导目的状语从句的连词或词组一般有:so that以便，in order that以便，in case免得;以防，for fear(that)惟恐;以免，lest & for fear that惟恐;以免;为不使；now that & given that因为。
e.g.
She wanted tea ready at seven so she could be by eight.
They started early so that they might arrive in time.
They stopped at Hangzhou in order that they could go around West Lake.
She explained again and again in case we should misunderstand her.
They spoke in whisper for fear (that) they might wake the baby.
Lest anyone should think it strange,let me assure you that it is quite true.
结果状语从句
结果状语从句一般由so,that,so that,so...that,such that等引导放在主句之后。
e.g.
He spoke so fast that nobody could understand what he was saying.
He made such repid progress that he soon began to write articles in English.
There is so little time left that I have to tell you about it later.
He told us such a story that we all laughed.=He told us so funny a story that we all laughed.
The shops were closed so I didn't get any milk.
He phoned me on arrival so that I knew he was safe and sound.
Suddenly it began to rain heavily,so that it was almost impossible to carry on driving.
注意：So that引导结果状语从句时：so that前常有逗号，从句中常无情态动词；引导目的状语从句时：so that前常无逗号，从句中常有情态动词。
方式状语从句一般由连词as(正如;就像),as if/though(好像;宛如)引导。
e.g.
Why didn't you catch the last bus as I told you to?
She enjoys all kinds of music,as I do.
Like me,she enjoys all kinds of music.
Nobody understands him like/as I do.
as if/though
e.g.
They looked at me as if/as though I were mad.
They look as if/as though they know each other.
比较状语从句
比较状语从句一般由than（比）,as...as(和...一样),not as/so...as...(和...不一样),the+形容词比较级/副词比较级+the+形容词比较级/副词比较级(越...越...)等引导。
e.g.
She likes reading better than (she likes) going to parties.
He has lived here longer than I (has lived).
They love the girl than (they love) him.
He has more friends than she (does).
Air in the country is much fresher than that in the city.
She is younger than me. <Spoken English>
You are more industrious than her. <Spoken English>
as..as 或 not so/as..as
e.g.
We were as fortunate as them (they were).
I hope she will make as much progress as you (have done).
She runs as fast as a boy (does).
the...the...
e.g.
