定语从句是指一类由关系词引导的从句,因为这类从句的句法功能多是做定语，所以曾被称为定语从句，这类从句除了可以做定语之外，还可以充当状语等其他成分，所以现代语言学多使用“关系从句”这一术语。下面为大家带来了定语从句中关系代词as的用法，欢迎大家参考！
一、AS引导限制性定语从句。
AS引导限制性定语从句时,通常和such,the same,as(so)等连用,构成such...as/such as,the same...as/the same as,as(so)...as等结构,在从句中可作主语,宾语和表语。
1.such...as/such as意为“...的那种...,像那样的”，such...as/such
as引导限制性定语从句时,既可指人,也可指物。such用于名词之前时,具有形容词性质;such单独使用(即后面不接名词)时,具有代词性质。
Don’t trust such men as praise you to your face.(as作主语)
不要相信那种当面吹捧你的人。
You should read only such books as you can understand without much difficulty.(as作宾语)
你应当只读那些你读起来不太难懂的书。
Associate with such as will improve your manners.(as作主语)
要和能改善你的言行的那种人结交。
2.the same...as/the same as意为“与...同样的”,和such一样,the same既有形容词作用,又有代词性质。
We have arrived at the same conclusoin as they have.(as作宾语)
我们已得出和他们同样的结论。
比较:the same...as和the same...that不同,前者是“同那一个相似”,后者是“正是那一个”。如：
This is the same watch as I lost.
这同我丢的那块表一样。
This is the same watch that I lost
这正是我丢的那块表。
3.as(so)...as意为“和...一样”,后接由many,much等修饰的名词或由形容词修饰的单数名词,注意其语序为as(so)+adj.+a+n+as,如：
It’s as pleasant a film as I have ever seen.
这是一部和我以往看的`同样好的电影。
As many soldiers as marched were killed.
很多**的战士都被杀了。
注意:such ...as与such...that ,so...as与 so...that的区别:
that是连词,引出结果状语从句,在从句部分不作成分;as是关系代词,引出定语从句,在从句中可作主语,宾语和表语。比较:
He is such a nice boy that everyone likes him.
He is such a nice boy as everyone likes.
It is so difficult a problem that nobody can work it out.
It is so difficult a problem as nobody can workout.
二、AS引导非限制性定语从句。
AS引导非限制性定语从句时,通常指的不是主句中的某一个名词(先行词),而是指整个主句表达的内容,对主句所作的陈述进行附加说明,意为“这...,如...或正如...”。这种从句可位于主句之前,之中或之后。
As we all know,hainan belongs to China.
hainan,as we all know, belongs to China.
hainan belongs to China,as we all know.
注意下面的习惯用法:
as is well discussed 正如已讨论过的
as is often said 正如通常所说
as is often the case 通常就是这样
as has been pointed 正如所指出的那样
as has been said before 如上所述
as often happens 如同经常所发生的那样
as might be expected正如所料
as is well known to all众所周知
在多数情况下,从句中的谓语助动词可以省略
as explained before 如前面所解释的
as mentioned above 如前面所提到的
as shown in the figure 如图所示
as seen from the table 从表中可以看出
as already discussed 正如已讨论过的
高考题精选：
1.______is known to all,China will be an and powerful country in 20 or 30 years’ time.(1994上海)
A.That;advancingB.This;advanced
C.As;advanced D.It;advancing
2.______is mentioned above,the number of the students in senior high schools is increasing.(1999上海)
A.It B.As C.That D.Which
3.These houses are sold at such a low price________people expected.
A.likeB.as C.that D.which
4.________is known to everybody, the moon travels round the earth once every month.(2001NMET)
A.It B.As C.That D.What
5.There at the door stood a girl about the same height __________.(2004北京春)
A.as me B. as mine
C.with mine D. with me
6.__________is reported in the newspapers, talks between the two countries are making progress.(2004北京)
A. It B. As C. That D. What
7._________is often the case, we have worked out the production
plan.(2004江苏)
A. Which B. When C. WhatD. As
8._______I explained on the phone,your request will be considered at the next meeting.
A.When B.AfterC.AsD.Since
9.The Beatles,_________many of you are old enough to remember,came from Liverpool.
A.what B.that C.how D.as
Keys:CBBBABDCD