【As在定语从句中的用法】

1. 引导限制性定语从句和非限制性定语从句

(1)as多与such 或the same连用，可以代替先行词是人或物的名词。

(2)as 也可单独使用，引导非限制性定语从句，作用相当于which。例如：

The elephant's nose is like a snake, as anybody can see.

(3)the same… that与 the same …as在意思上是不同的。

2.As引导的非限制性定语从句的位置

as引导的非限制性定语从句位置较灵活，可以位于主句前面、中间或后面，一般用逗号与主句隔开，但which所引导的非限制性定语从句只能放在主句之后。例如：

(1) As is expected, the England team won the football match.

(2) The earth runs around the sun, as is known by everyone.

【关系副词引导的定语从句】

1.关系副词也可以引导定语从句

关系副词在从句中分别表示时间、地点或原因。关系副词when在从句中充当时间状语，where 充当地点状语，why充当原因状语。

2. that可引导定语从句表示时间、地点或原因

That有时可以代替关系副词 when, where 或者why引导定语从句表示时间、地点或原因，在 that引导的这种定语从句中，that也可以省去。

【关系代词引导的定语从句】

1.who指人，在从句中做主语

(1)The boys who are playing football are from Class One.

(2)Yesterday I helped an old man who lost his way.[page]

2. whom指人，在定语从句中充当宾语，常可省略。

(1) Mr. Liu is the person (whom) you talked about.

注意：关系代词whom在口语和非正式语体中常用who代替，可省略。

(3) The man who/whom you met just now is my friend.

3. which指物，在定语从句中做主语或者宾语，做宾语时可省略

(1) Football is a game which is liked by most boys. ( which 在句子中做主语)

(2) This is the pen (which) he bought yesterday. ( which 在句子中做宾语)

4. that指人时，相当于who或者whom;指物时，相当于which。

在宾语从句中做主语或者宾语，做宾语时可省略。

(5) The people that/who come to visit the city are all here. (在句子中做主语)

(6) Where is the man that/whom I saw this morning? (在句子中做宾语)

5. whose通常指人，也可指物，在定语从句中做定语

(1) He has a friend whose father is a doctor.

(2) I lived in a house whose roof has fallen in.

whose指物时，常用以下结构来代替

(3)The classroom whose door is broken will soon be repaired.

=The classroom the door of which is broken will soon be repaired.

(5)Do you like the book whose color is yellow?

=Do you like the book the color of which is yellow?