定语从句中as的用法
定语从句就是在整个句子中充当定语的句子修饰名词或代词，被修饰的名词词组或代词即先行词。定语从句通常出现在先行词之后，由关系词（关系代词或关系副词）引出，小编在这里特意为大家整理了关系代词as的用法，一起来看一下吧！
1. 准关系代词as引导限制定语从句，用于以下3个结构中，as在从句中作主语、宾语或表语：
a. so / such…as
Such people as were mentioned by him were honest. (as作主语)
I’ve never seen such a clever man as he is. (as作表语)
Last term our maths teacher set so difficult an (= such a difficult) examination problem as none of us worked out.
b. the same…as
Modern statemen are often faced with the same problem as defeated the ancient Romans. (as 作宾语)
I like the same book as you do. (as 作宾语)
c. as…as
As many children as came were given some cakes. (as 作主语)
He is as diligent a man as ever lived. (as 作主语)
补充：
a. such…as 与 such…that的区别
such…as 引导定语从句;such…that引导结果状语从句。
They talked in such simple English as children could understand.
他们用孩子们能听懂的简单的英语交谈。
They talked in such simple English that children could understand it.
他们用十分简单的英语交谈，连孩子们都能听懂。
I will provide you with such things as you may need.
我要供给你一些你可以用得着的东西。
He shut the window with such a force that the glass broke.
他如此用力地关门，结果玻璃碎了。
b. the same…as与the same…that的区别：
the same…as指两物相似，the same..描述的是同一物。
This is the same bag as I lost yesterday.
这个书包和我昨天丢失的(书包)相似。(相似物)
This is the same bag that I lost yesterday.
这正是我昨天丢失的那个书包。(同一物)
2. 准关系代词as引导非限制定语从句。
a. as引导非限制性定语从句，只代表主语或主句的一部分所表达的意思(不能指代某个名词或代词)，可以放在主句前，后或中间，在从句中作主语或宾语、例如：
As is known to all, he is the best student in our class. (as指代整个句子，作主语，置于句首)
He opposed the idea, as could be expected. (as 指代整个句子，作主语，置于句末)
As we all know, he studies very hard. (as 指代整个句子，作宾语，置于句首)
Taiwan is, as you know, an inseparable part of China. (as指代整个句子，作宾语，置于句中)
常用的这类句式有：
as is said above 综上所述 - as is known to all 众所周知
as is often the case 通常如此 - as is reported in the newspaper 如报纸所报导的
b. 主句具有否定意义，as引导的定语从句位于主句之后时，as指代得主句不包括否定意义，并可用but取代。例如：
Whales are now fish, as some people think / but some people think they are.
I am no orator, as Brutus is.我不善言词,而勃鲁特斯却是个雄辩家.
Spiders are notinsects,as many people think, nor even near1y related to them.
蜘蛛不是昆虫,尽管许多人认为它是昆虫,它甚至与昆虫几乎没有关系.
但as引导的定语从句谓语主句前时，as指代的主句仍包括否定意义。
As has been said above, grammar is not a set of dead rules.
正如前面所说的，语法不是一套死条纹。
3. 在非限制性定语从句中，which和as引导定语从句时的区别：
a. which引导的从句不能放在主句前，而as引导的从句则既可以放在主句前，也可以放在主句后。
b. 用能做关系代词，as和which都可以指代一个句子，但as有“正如”、“就像”之意，which则没有此含义。
He is a foreigner, as I know from his accent. (as指代一个句子，意为“正如”、“就像”)
He has to work on Sunday, which he doesn’t like. (which指代一个句子，没有“正如”、“就像”)
c. 当从句的谓语动词是be或相当于联系动词的seem, become等时，可用as或which作主语。但当从句的谓语是行为动词时，只能用which作主语。
4. as 可用作连词，引导状语从句，构成省略形式“as + 过去分词”这一特殊结构，译成汉语时作用如定语。例如：
The bridge as shown in the picture is really wonderful. (as shown = as it is shown 可译为“图中的桥”)
See the answers as given at the end of this book. (as given = as it is shown 可译为“书后给出的答案”)
English as spoken is Australia is slightly different from British English.
(as spoken = as it is spoken 可译为“在澳大利亚讲得英语”)
请看下列的“as + 过去分词”结构用于修饰前面的名词：
The study as described in the article… 如文章中描述的那种学习
The program as conducted by… 由…指挥的(指导的)节目
The art as applied to medicine… 应用于医学的艺术
The products as seen on TV…电视上看到得产品
定语从句中that的用法
1. 不用that的情况
(1) 在引导非限定性定语从句时。
(错)The tree, that is four hundred years old, Is very famous here.
(2) 介词后不能用。
We depend on the land from which we get our food.
We depend on the land that/which we get our food from.
2. 只能用that作为定语从句的关系代词的情况
(1) 在there be 句型中，只用that，不用which。
(2) 在不定代词，如：anything, nothing, the one, all等作先行词时，只用that，不用which。
(3) 先行词有the only, the very,the same,the last,just修饰时，只用that。
(4) 先行词为序数词、数词、形容词最高级时，只用that,不能用which。.
(5) 先行词既有人，又有物时。
(6) 先行词指物，在主句中作表语时.
(7) 为了避免重复.
(8) 先行词是the way或the reason时，that可作关系副词，也可省略
(9) 主句的主语是疑问词who /which时
定语从句中的that和which用法区别
that和which在从句里都可以做宾语和主语，做宾语时可以省略。在定语从句中,有种说法叫"关宾省"，意思是关系代词在限制性定语从句中作宾语可以省略，不管是that，which，还是whom。但是which能引导非限制性定语从句，that则不行。
记得以下只能用that的几种情况：
1. 当先行词为all, much, little, none及由any, every, some, no所构成的复合不定代词时。
如：
Please tell me anything that you know about the matter.
有关此事，凡是你所知道的请告诉我。
2. 当先行词被any, few, little, no, all, much, some等词修饰时。
如：You can take any seat that is free.
任何空着的座位你都可以坐。
3. 当先行词为序数词或被序数词所修饰时。
如：
This is the fourth film that has been shown in our school this term.
这是我们校本学期放映的第四部电影。
4. 当先行词为形容词最高级或被形容词最高级修饰时。
如：
This is the most interesting story book that I have ever read.
这是我读过的一本最有趣的故事书。
5. 当先行词被the very, the only, the last, the just, the same等修饰时。
如：
The only thing that we could do was to wait.
我们唯一能做的事就是等待。
注意：先行词被the same修饰时，关系代词也可用as。
如：I need the same book that / as you have.
我需要有你一样的书。
6. 当先行词既包含人又包含物时。
如： They are talking of the heroines and their deeds that interest them.
他们正在谈论他们感兴趣的女英雄及她们的事迹。
7. 当先行词是疑问代词who，which，what或主句以这些词开头时。
如：
Who that has ever worked together with him doesn’t admire him?
曾经和他一起工作过的谁不钦佩他？
8. 当先行词为主句表语或关系代词为从句表语时。
如：
Our school is no longer the place that it used to be.
我们的学校现在已不是过去的那个样子了。
9. 先行词为time时，当time表示次数，引导词用that, 可省略。 当表示时间，可用that或when引导，都可省略。
如：
I didt remember the exact time （when/that） I arrived in Shanghai last month.
我不记得上个月到达上海的确切时间了。
请注意以下几种只能使用which的情况:
1. 在“介词＋关系代词”结构中，关系代词必须用which。
如：
This is the reference book of which the teacher is speaking.
这就是老师正在谈及的那本参考书。
注意： 如果介词不放在修饰事物的限定性定语从句的句首， which就可换为that，例如：
This is the question which/that we’ve had so much discussion about. =This is the question about which we’ve had so much discussion.
这就是我们已经多次讨论过的问题。
2. 先行词为“those＋表事物的复数名词”时， 关系代词通常只用which而不用that。
如：You should grasp well those skills which may be used in the future work.
你应该掌握好这些可以用到未来工作中的技能。
最后，记得这个特殊情况吧：当先行词是表示原因或方式的名词时，可以用that引导定语从句，相当于介词+which，that可以省略。
如：
He didn’t like the way that (=in which) she speaks to his mother.
他不喜欢她对他的母亲那样说话。
Imagine the speed that (=at which) he drives the car.
很难想象，他开车开得那么快。
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