6、which 引导非限制性定语从句，指代主句中的一个词(先行词)从句置于先行词后，可在句中或句尾。

The football match, which I watched yesterday, is very interesting.

5、which 引导非限制定语从句，指代整个主句的内容，从句只能置于句尾。

The decision was postponed, which was exactly what he wanted.

4、as引导非限制性定语从句，有“正如”的含义，因此，下列句式中多用as:

as has been said above　　　　　 as anybody can see　　　　　　　 as we had expected　　　　　　　 as (it) appears

Things are not always as they appear.

3、非限制性定语从句中谓语为被动时，常用as 作主语。

as is said/ known/ announced/ reported/ mentioned/ expected/ disused等。

As is known to all, Taiwan is part of China.

2、as 引导非限制性定语从句，指代整个主句的内容，从句可置于句首，句中和句尾。

As everyone knows, Tom is good at English.

The earth, as we know, moves round the sun.

1、用于非限制性定语从句时，可以指代整个主句的内容，as 和which 可以换用。

He left her, as/ which was strange.

·限制性定语从句对先行词起限制确定作用。如果没有它，主句的意思就不完整，这种定语从句和主句的关系十分密切，不可用逗号隔开，在口语中前后没有停顿。

He is the man whose father died last week.

That is the reason why I didn’t open the door.

·非限制性定语从句与主句的关系不十分密切，只是对先行词起描述或补充说明的作用，省略后也不影响全句的意思，非限制性定语从句可以修饰名词、代词、短语、主句的一部分或全句，它和主句之间常用逗号隔开，朗读时前后有停顿。

I live in Beijing where my parents worked ten years ago.

His sister, who works in WuHan, is coming to see him tomorrow.

6、介词+whose 修饰后面的名词：He is the very man in whose pocket I found my lost money.

5、介词+关系代词+代词/数词：He has written many books, of which most are in Chinese.

4、代词/数词+of +关系代词

He has written many books,　 most of which are for children.

We have many students, two of whom have won prizes of international competitions.