一、状语从句
主句更重要，从句次之。
状语从名不修饰名词，它表示一种关系。即主句和从句之间有明显的关系。
一个句子可以有多个状语从句。（通常一个句子以状语从句开始，人要加一个“,”）
Although I love pizza, I rearly eat it because it's unhealthy.
（三）解说
其实就是表示时间、地点、（原因、结果）、（条件、目的）、（相反、比较）等。
1. 时间 （过去、现在、未来分别对应after、when、before)
when he was a young man, he was forced to leave his homeland.
Some babies learn to swim even before they are one years old.
2. 地点 Where there is a will, there is a way.
3. 原因 见上面
4. 条件 If you ask him,he will help you.
5. 目的 You must speak louder so that /in order that you can be heard by all. （和主+谓+宾+to+介词 的句式比较像）
6. 让步： 见上面的although
7. 比较 My hometown is as/so beautiful as Hangzhou
8. 方式 He looks as if he is angry.
9. 结果 He made such rapid progress that before long he began to write articles in English for an American newspaper. In fact, his English in one of these articles was so good that Engels wrote him a letter and praised him for it.（such 是形容词，修饰名词或名词词组，so 是副词，只能修饰形容词或副词。）
(二）一些例句
If you have recently added your website to Bing Webmaster Tools, it might take a few days before you see Search performance data for your website.
I am not as able to do this as she is.
Joe took a week off work so that his wife could take a training course.
状语从句里面又有状语从句：
You should stay home because if you go (there) there will be trouble.(there是主语，will是verb)
二、定语从句
修饰名词，它提供这个名词的额外信息或者修饰这个名词。
（一）限制性定语从句
是不可缺少的定语，不用逗号分开。
I was the only person in my office who was invited.
（二）非限制性定语从句
只对先行词作些附加说明，如果去掉，主句的意思仍然清楚。用逗号隔开，一般不用that引导。
Abraham Lincoln, who led the United States through these years, was shot on April 14, 1865 at a theatre in Washington , D.C.
Gealileo lived in the city of pisa, where there is a leaning tower about 180 feet high.
关于that\which
1.限制性定语从句，用that, 没有逗号，非限制性定语从句，用which，有逗号。
2.有的老师会说一样的，两个都可以用。但是参加考试的时候，要按上面的要求。
what 只能用于名词性从句。
三、名词性从句
1.作主语
2.作宾语、主语补足语
作宾语时，answer what or whom about the Verb
作主语补足语时，answer what or whom about the subject（就是表语）
3.放在介词后面。（不是作动词的宾语，而是作for的宾语）
4.形容词的补语
四、compound complex 并列复合句（复合句+三大从句）
