一．原因从句
1. 由as／because／since 引导的原因从句：
We camped there as／because／since it was too dark to go on．我们在那里露宿是因为天太黑，不能再继续往前走了。
As／Because／Since it was too dark to go on，we camped there．因为天太黑不能再继续往前走，我们就在那儿露宿了。
2. in view of the fact that可用as／since／seeing that来表示，但不能用because： As／Since／Seeing that you are here，you may as well give me a hand．既然你在这儿，就帮我个忙吧。
As／Since／Seeing that Tom knows French，he'd better do the talking．既然汤姆懂法语，最好让他来谈。
二．结果从句
结果状语从句——引导结果状语从句的连词有：so that, so…that, such that, such…that, that等。当从句前面有逗号时，so that中that可省略，如：
It was dark, so (that) we could see nothing in front of us.
“So + 形容词 / 副词 + that”是引导结果状语从句的常用结构，如：
He talked so loud that he annoyed the speaker. He was so brilliant that he made a lot of inventions.
“such (a) + 形容词 + 名词 + that”与“so…that”的意义相同，如：
It was such a hot day that people could not go out. He painted such beautiful pictures that the visitors were lost in admiration.
such／so…that引导的结果从句
A such是形容词，用于形容词+名词结构之前：
They had such a fierce dog that no one dared to go near their house．他们有一条如此凶猛的狗，以致没人敢靠近他们家。
He spoke for such a long time that people began to fall asleep．他说了这么长时间，以致在座的人都犯困了。
B so是副词，用于副词和不带名词的形容词之前：
The snow fell so fast that our footsteps were soon covered up．雪下得这么快，以致我们的脚印很快就被雪盖住了。
His speech went on for so long that people began to fall asleep．他的讲话这么长，以致在座的人都开始犯困了。
Their dog was so fierce that no one dared come near it．他们的狗太凶猛了，所以没人敢靠近它。
such不能用于much和many之前，so可用于后跟名词的much和many之前：There was so much dust that we couldn't see what was happening．灰尘太大了，使得我们看不清发生了什么事。
So many people complained that they took the programme off．抱怨的人太
多，所以他们取消了那个节目。．
C 注意：such＋a＋形容词＋名词可由so＋形容词＋a＋名词来代替，所以such a good man可由so good a man来代替。这只能在名词前面有a／an的情况下使用。
热点之一：含有否定意义的副词放在句首引起的部分倒装
此类副词有：not，never，seldom，hardly，rarely，little等。例如：
Not a single word did he say at the meeting．（在会上，他什么也没说。）
热点之二：含有否定意义的连接词置于句首引起的部分倒装
此类连接词有：not only．．．but also，neither．．．nor．．．，no sooner．．．than，scarcely．．．when，hardly．．．when等。请看例句：
No sooner had she gone out than the telephone rang．（她一出门电话就响了。）
热点之三：搞清so（nor ，neither）＋助动词＋主语与so（nor ，neither）＋主语＋助动词之间的区别
前者表示重复前句部分的内容，译为“也是如此”。而后者表示对前句内容的进一步肯定或证实，译为“确实如此”。例如：
Lily can't answer the question．Neither can I．莉莉不能回答这问题。我也不能。
Tom was late for school yesterday．So he was. 汤姆昨天上学迟到。他确实如此。
热点之四：省略if的虚拟条件句以had ／were ／should开头引起的部分倒装这是虚拟语气中比较特殊的一种，其实质就是省略if后引起的变化。如：
Had he worked harder，he would have got through the exams．（要是他努力学习的话，他是会通过考试的。）
热点之五：not until置于句首引起后面句子的部分倒装
not until意为“直到……才……”，位于句首时引起后面的主句倒装。如：
Not until the teacher came did he finish his homework．老师来了他才完成作业。
热点之六：only短语置于句首引起的部分倒装
only放在句首，修饰副词、介词短语或状语从句，常引起后面句子部分倒装。如：
Only in this way can you learn English well．只有通过这种方式，你才能把英语学好。
让步从句
它们由下列词来引导：although，though，even though，even if，no matter，however有时也可以使用whatever。as也可以，但是只限于形容词＋as＋be结构。
Although／Though／Even though／Even if you don't like him you can still be polite．尽管／即使／纵然／即使你不喜欢他，你仍可有礼貌一些。
No matter what you do，don't touch this switch．无论怎样，都别碰这个按钮。
However rich people are，they always seem anxious to make more money．无论人们多么富有，他们似乎总还渴望赚到更多的钱。
However carefully you drive，you will probably have an accident eventually．无论你开车多小心，最后你大概还会出车祸。
Whatever you do，don't tell him that I told you this．无论如何，别跟他说这件事是我告诉你的。
Patient as he was，he had no intention of waiting for three hours．哪怕他再有耐心，也不打算等上三个小时。
比较从句
He didn't play as well as we expected／as well as you（did）．他打得不如我们预料的好／你打得好。
He sings more loudly than anyone I've ever heard／than anyone else （does）．他唱得比我听到的任何人唱得都响／比任何人都声音响。
You work harder than he does／than him／than I did at your age．你比他干得卖劲／我在你这个年龄时干得卖劲。
时间从句
A 时间从句由下列表示时间的连词来引导：
after immediately till／until no sooner…than when as soon
as since whenever before the
sooner while hardly…when the minute the moment
B 时间从句中不用将来时态。
1 如将下列将来时态放入时间从句中，须将它变为一般时态。
You'll be back soon．I'll stay till then．= I'll stay till you get back．你会很快回来，我一直等到那时。
C since从句
since从句后面常跟完成时态
They've moved house twice since they got married．／Since they got married，they've moved house twice．他们结婚后已搬了两次家。
He said he'd lived in a tent since his house burnt down．他说自从他的房屋被烧毁后，他就一直住在帐篷里。
It's ages since I sailed／have sailed a boat．我未驾驶帆船已有好多年了。
I haven't sailed a boat since I left college．自从我大学毕业后就没再驾驶帆船了。
D after从句
after从句之后常跟完成时态：
After／When he had rung off I remembered…等他把电话挂断后，我才想起……
After／When you've finished with it，hang it up．你用完了之后，请把它挂起来。
E hardly／scarcely… when，no sooner… than
The performance had hardly begun when the lights went out．= Hardly had the performance begun when the lights went out．演出刚开始就停电了。
这里可以用scarcely代替hardly，但不常见。
He had no sooner drunk the coffee than he began to feel drowsy．= No sooner had he drunk the coffee than he began to feel drowsy．他喝咖啡没多一会儿，就犯困了。
He no sooner earns any money than he spends it．= Immediately he earns any money he spends it．他钱一挣到手，就花光了。
注意the sooner…the sooner的用法：
The sooner we start，the sooner we'll be there．我们动身得越早，到那儿就越早。