1、 名词性从句, 细分又分为主语从句,宾语从句,表语从句和同位语从句
What he wants is his mother’s love.
I don’t know how to answer the question.
This is why I came here.
I have no idea where he born.
引导定语从句的关系代词有who, whom, whose, which, that, as,和关系副词when, where, why。
关系词 先行词 从句成分
关系代词 who 人 主语
whom 人 宾语
whose 人，物 定语
that 人，物 主语，宾语
which 物 主语，宾语
as 人，物 主语，宾语
关系副词 when 时间 时间状语
where 地点 地点状语
why 原因 原因状语
a. 先行词有all, everything等不定代词时，如，
Everything (that) he did is right.
b. 先行词被all, every, no, some, any, little, much等修饰时，如，
I’ll read all the books (that) you lend me.teacheray.com
This is the first letter (that) the boy has read.
d. 先行词被the only, the very, the same, the last修饰时，如
He is the very man (that) I’m looking for.
（2）where, when, why作关系副词
I’ll never forget the day when I first came to Beijing.
I’ll never forget the days that/which we spent together.
Hangzhou is a city where there is a beautiful lake.
Hangzhou is a city which/that has a beautiful lake.
We don’t know the reason why he was late yesterday.
The reason which/that he gave was reasonable.
as 可以放于句首，而which 不可以, 如果有“正如，象”的含义，并可以放在主句前，也可以放在后面，那么用as；而which引导的从句只能放主句后，并无“正如”的意思。
They won the game, as we had expected.
They won the game, which we hadn’t expected.
As is well known, he is a famous film star in the 1990s.
（4）three of them 和three of which
I have a lot of books, three of which are in English.
I have a lot of books and three of them are in English.
○1 时间状语从句：由when, while, as, the moment, the minute, whenever, before, after, till(until), since, as soon as等连词引导。
You must look left and right when you cross the crossing .
○2 条件状语从句：由if, unless, as long as, in case , if only, provided that等引导。
I’ll show you around the city if I am free tomorrow .
○3 原因状语从句：由because, as, since, for（因为）等引导。
He was absent yesterday because he was ill .
As it was already dark, they decided to stay in the town for the night .
○4 目的状语从句：由so that, in order that, in case等引导。
He got up early so that he could catch the early train.
○5 结果状语从句：由so…that, such…that等。
The film is so interesting that everyone wants to see it again .
○6 比较状语从句：由than, as…as, not as(so)…as, the（＋比较级）…the（＋比较级）等引导。
Today is not as warm as yesterday.
○7 地点状语从句：由where 和wherever等引导。
He follows her wherever she goes .
○8 方式状语从句：由as, as if 等引导。As if 引导的从句的时态不符合事实时要用虚语语气。
Please do as I do .
He tells me the whole thing as if he knew everything .
○9 让步状语从句：由though, although, even if, even though, however, no matter wh+等引导。
Although he has failed many times, he doesn’t give up trying .