as 在定语从句的用法
as 在定语从句的用法1
一、as引导定语从句与其它词连用
A．用于the same．．．as．．．结构中
This is the same sickle as I lost yesterday．这把镰刀和我昨天丢的那把一样。
We drove out of the town by the same road as we had entered by．我们沿着进城的同一道路开车出城。
This is the same material as is used in building the bridge．这和建那座桥所用的材料一样。
注意：在这一结构中，as有时可以由that代替。例如：
I live in the same district as ／that he lives in．我和他住在同一区。
但两者亦有区别：
1．当定语从句省略谓语部分时，要用as。例如：
She uses the same scent as you（do）／that you do．她用的香水和你的一样。
This book of his is the same as yours．他的这本书和你的那本一样。
2．在容易引起歧义时，慎用as和that。例如：
This is the same knife as I lost last week．
（一般理解为：这把刀和我上周丢的那把相似。也可理解为：这是我上周丢的那把刀。）
This is the same knife that I lost last week．这是我上周丢的那把刀。
3．that在现代英语中可作关系副词，而as则不可。例如：
I live in the same district that he lives．（不可用as。）
B．用于such．．．as．．．结构中
I never heard such stories as he tells．我从未听过像他讲的那种故事。
He was in such a fury as I've never seen．他怒气之大，我从没见过。
Such women as knew Tom thought he was charming．认识汤姆的女人都认为他很有魅力。
注：有时such和as连在一起用。例如：
We had hoped to give you a chance such as nobody else ever had．我们本希望给你一次别人不曾有过的机会。
We are living in a new era such as has never existed before．我们生活在前所未有的新时代。
C．用于“so＋adj．＋a（n）＋n．（单数）＋as结构中
We witnessed so great a parade as nobody ever dreamt of in preliberation days．我们见到在解放前没有人曾经梦想过的一次盛大的。
I'm not so strong a man as I was．我已不像从前一样健康了。
He's never written again so good a book as his first one．他再也没写出像他的第一部那么好的书。
D．用于“as＋adj．＋n．＋as比较结构中
He is as learned a professor as works in the uni- versity．他是在这所大学工作的教授中最有学问的一个。
Some people have no doubt that their cat understands as many words as does a dog．许多人相信他们的猫跟狗懂的话一样多。
They are as fine women as ever walked．她们可以与任何卓越的女性媲美。
注：as．．．as．．．后面加上ever以加强语气，表示“不亚于任何……”，“不弱于……”，有最高级的意味。又如：
He is as brave a man as ever lived．他是世界上最勇敢的人。
二、as单独引导定语从句
A．as单独引导定语从句时，先行词可以是一个词，但更为常见的是：它的先行词是整个主句，有时也可以是一个短语。例如：
The two brothers were satisfied with this decision，as was agreed to beforehand两兄弟对此决定都很满意，这项决定事前已得到他们的同意。（先行词是decision）
She is late，as is often the case．她迟到了，这是经常的事。（先行词是整个主句）
He married her，as was natural．他和她结婚了，这是很自然的。（先行词是整个主句）
To shut your eyes to facts，as many of you do，is foolish．视而不见———你们好多人都是如此———是愚蠢的。（先行词是整个不定式短语）
B．as与which的区别
三、as引导定语从句的用法比较
1.as作为关系代词可以引导限制性定语从句， 主要用于such...as，the same...as，so...as，as...as等结构中。例如：
（15）Let’s deal with such problems as concern us.
（16）The purpose of the conductor is to transmit the electrical energy with as little loss as is practicable.
（17）There are so many tickets available as are asked for.
（18）She wears the same watch as I do.（同一类）
（19）This is the same watch that I lost yesterday.（同一个）
在（15）句中，as指代such修饰的名词“problem”，并在从句中作主语成分；（16）句中，第二个as指代第一个as所修饰的“little loss”; （17） 句中as 指代so 修饰的名词“tickets”; 在（18） 句中，as 指代“the same” 修饰的名词“clothes”， 在从句中作宾语； 此情况下不能用that和which来代替as引导定语从句。
比 较：在（18）句中，as指代的先行词表同一类，强调种类一样。而在（19）中that指代的先行词虽然也被“the same”修饰，但是此时先行词表示同一个。
2.as和which引导非限制性定语从句比较。
as和which都可以引导非限制性定语从句，代替整个句子。但是具体使用方法是有区别的，请看下面的例句比较：
（20）As we known，Yao Ming is the most famous basketballplayer in China.
（21）The number of the people，as we had expected，was overthree thousand.
（22）The sun gives off light and warmth，which makes it possiblefor living creatures to grow.
（23）She is very beautiful，which makes others jealous.
（24）She is very kind to the children，which her husband seldomwas.
（25）He became a teacher，which I was not.
在（20）句中as放在了句首，所指代的内容就是后面的一句话“Yao Ming is the most famous basketball player in China”；（21）句as放在了句中，同样指代的是一句话“The numberof the people was over three thousand”。从这两个例句中我们发现as引导的从句和主句在内容上表示一致， 或者说从句的内容是顺着主句的意思说下来的，有“就像”、“正如”之意。再看一下（22）句和（23）句，which的位置放在了句中，并且which引导的非限制定语从句是主句造成的一种结果。比如我们在翻译（22）句时可以这样理解：太阳释放出光和热，这使生物生长成为可能；当然（23）句我们也可以这样翻译：她很漂亮，这使其他人和嫉妒。从（24）句和（25）句我们还可以看到which引导非限制性定语从句的另一种用法，即which引导的非限制定语从句与主句内容不一致， 或起对立、否定关系。
四、as引导状语从句的用法比较
1.as，when和while作为连词引导时间状语从句的比较。
若主、从句表示两个同时进行的持续性动作，且强调主句表示的`动作延续到从句所指的整个时间， 通常要用while。但是，若主、从句表示的两个同时进行的动作含有“一边……一边”的意思，通常要用as。例如：
（26）Don’t talk while you’re eating.
（27）I kept silent while she was reading.
（28）She sang as she went along.
若从句是一个短暂性动作，而主句是一个持续性动作，一般用when。如果主、从句表示的是两个同时（或几乎同时）发生的短暂性动作，一般要用as。例如：
（29）When he came in，I was watching TV.
（30）It was raining hard when he arrived.
（31）I had guessed it just as you opened your mouth.
若要表示两个正在发展变化的情况， 相当于汉语的“随着”，一般用as。表示“每当……的时候”（暗示一种规律性），一般要用when。例如：
（32）Situations are getting better and better as time goes on.
（33）As it grew darker，it became colder.
（34）It’s warm when sun shines.
（35）He smiled when I praised him.
2.as，though 和although 作为连词引导让步状语从句的对比。
as引导让步从句时，句子必须倒装。常把被强调的作表语的形容词、名词及作状语的副词放句首，有时甚至把谓语动词放句首。though引导让步状语时，句子可以倒装（倒装方式和as一样）也可以不倒装。although引导让步状语时，只能用正常语序，不能倒装。下面我们看一下例句（36）—（39）：
（36）Poor as/though they are，they are very ambitious.
（37）Child as/though he is，his behavior seems mature.
（38）Hard as/though he worked，he didn’t pass the exam.
（39）Try hard as/though he will，he is not successful.
3.as，because，since 和for 作为连词引导原因状语从句比较。
because引导原因状语从句时语气最强， 常表示必然的因果关系，从句是全句的重心，它引导的从句一般放在主句的后面， 并且回答以why引起的特殊疑问句；as只说明一般的因果关系，语气比because弱，说明比较明显的原因，它引导的从句通常放在句首，常意为“由于”；since意为“既然”，表示对方已经知晓，无需加以说明的原因或事实（有时为天经地义的事实或格言、谚语等），语气比because稍弱，全句重点落在主句上；for是并列连词，它的语气最弱，常用来补充说明理由或提供一种解释，一般放在句中，强调“理由”。下面我们看一下例句再一次进行比较。
（40）He is absent today because he is ill.
（41）As everyone has arrived，we can set off now.
（42）I’ll do it for you since you are busy.
（43）We must leave now，for the film begins at seven.
4.as引导的方式状语从句用法。
as，（just） as...so...引导的方式状语从句通常位于主句后，但在（just） as...so...结构中位于句首，这时as从句带有比喻的含义，意思是“正如”、“就像”，多用于正式文体，例如：
（44）I shall do the exercises as you have been taught.
（45）As water is to fish，so air is to man.
（46）Just as we sweep our rooms，so we should sweep old ideas from our heads.
总之， 社会和英语语言的不断发展给英语语法的归纳和研究带来了很大的挑战，也给语言学习者带来了很多困难，但不管怎样，只要我们在学习过程中不断探索、勇往直前，一定能找到其中的规律， 帮助英语学习者消除英语学习中的重重障碍。
as 在定语从句的用法2
定语从句as的用法
一、用作连词的as
1. 引导时间状语从句，表示“当……的时候”，其用法与when和while类似。例如：As a child (When he was a child), she was sent to six different schools.此用法中as多表示从句与主句动作同时进行，意为“一边……一边……”，一般不与状态动词连用。例如：She sang songs as she did her homework.
as 还可以表示一动作紧接着另一动作发生，说明另一动作的结果，有“随着……”的含义。例如：As time went by, we found he was an honest man./As he grew older, he lost interest in everything except gardening.
例1 It wasn’t until nearly a month later________ I received the manager’s reply.
A. since B. when C. as D. that
解析：本题的as中与when一起作为干扰项，容易使考生往时间状语从句上思考，事实上本题是强调句，正确选项是D。
2. 引导原因状语从句，表示“由于，因为”，相当于because, 但通常置于句首。例如： As he is a qualified doctor, I trust his advice on medical matters.
例2 _____ modeling business is by no means easy to get into, the good model will always be in demand.
A. While B. Since C. As D. If
解析：本题中as干扰性很强，很多考生误以为是原因状语从句，但仔细分析不难发现正确答案应是A(while表示“只要”)。
3. 引导让步状语从句，通常可与although或though通用，但语序不同，although或though用于句首，as用于倒装结构。例如：Young as I am, I already know what career I want to follow. /Although(或Though)I am young, I already know what career I want to follow. as 表示让步用于倒装结构，通常将从句的表语、状语或动词前置。如果表语有冠词a/an, 需去掉。例如：Great scholar as he is, he is lacking in common sense./Much as I like you, I couldn’t live with you. 例3 _____ he has limited technical knowledge, the older worker has a lot of experience.
A. SinceB. Unless C. As D. Although
解析：as 虽然有引导让步状语从句用法，但本题不是倒装结构，故正确答案应是D。
4. 引导方式状语从句，表示“如，像”。例如：When in Rome, do as Romans do./Do to others as you would have others do to you.
例4 We wanted to get home before dark, but it didn’t quite ________ as planned.
A. make outB. turn out C. go onD. come up
解析：本题考查动词词组辨析，题干中的“as planned”给同学们提供了重要信息，答案选B。
5. 固定句型：“主句，as +be/do+主语”表示“也一样”。例如：She’s unusually tall, as are both her parents./He’s a doctor, as was his wife before she had children.
二、用作介词的as
1.表示“如，像”。例如：They got united as one man./She spoke of me as her dearest friend.
2.表示“作为、当作”。例如：As a League member, you should think more of others.
3.与某些动词搭配，表示“把……当作……”，如：look on…as…, regard…as…, treat…as…, consider…as…, think of…as…, see…as…等。其中consider…as…中的as可以省略。as与famous或known搭配，表示“作为……而出名”。
例5 Linda worked for the Minnesota Manufacturing and Mining Company, ________ as 3M.
A. knowingB. known C. being knownD. to be known
解析：如果熟悉be known as这一短语，运用有关非谓语动词的常识，可选出正确答案B。
三、用作关系代词的as
1. 引导限制性定语从句，先行词前通常有as, so, such, same等修饰语。例如：He will marry as pretty a girl as he can find./My hometown is no longer the same as it used to be./As many people as are present will be given a present.在此种用法中，同学们要注意与结果状语从句的区别。比如：A: The teacher asked us such a difficult question that none of us could answer it. B: The teacher asked us such a difficult question as none of us could answer.A句为结果状语从句，而B句则是定语从句。
2. 引导非限制性定语从句，用来指代整个主句(即先行句)，表示“这一事实，那一情况”。从句可以位于句首、句中或句末。例如：We stand when the national anthem is played, as is the custom.
例6 ______ I explained on the telephone, your request will be considered at the next meeting.
A. When B. After C. As D. Since
解析：根据句意，选项C是正确答案。as表现的正是本点所讲用法。
四、用作副词的as
修饰形容词或副词，表示程度，意为“同样地”。例如：He swims fast, but I swim just as fast. 但它通常构成表示比较的结构“asas”，“not asas”。此结构中第一个as是副词，第二个as是连词。否定结构中的副词as可以由so代替。asas possible /one can也属于此用法。例如：It is generally believed that teaching is as much an art as it is a science.
五、用在习语中的as
由as构成的习语很多，常见的有：as soon as “一就”，引导时间状语从句;as/so long as “只要”引导条件状语从句;as if/though “好像，仿佛”，引导方式状语从句或表语从句;as to/ as for “至于，就而言”;as much/many as“多达”;as/so far as “就的限度”;as a result，as a result of “(由于的)结果”;as a matter of fact“事实上”;as well “也、还”;A as well as B“不但A而且B”;as it is“照现状看，看样子”，等等。这些习语在高考中可能经常遇到，在高考题中有的作为正确选项，有的作为干扰项，有的出现在题干，值得同学们认真掌握。例如：
例9 I would like a job which pays more, but ______ I enjoy the work I’m doing at the moment.
A. in other wordsB. on the other hand C. for one thing D. as a matter of fact 解析：选项D极具干扰意义，但进一步研读会发现本题中的两个分句表达了一件事的两个对立面，故选B。
例10 ——People should stop using their cars and start using public transport. ——______. The roads are too crowded as it is.
A. All right B. Exactly C. Go aheadD. Fine
解析：本题选项中虽没有as内容，但题干中的as it is却是解题的关键信息，正确选项为B。
as 在定语从句的用法3
as在定语从句中是十分常见的，那么as引导定语从句的用法又是什么呢?
as作关系代词时，引导定语从句在从句中充当主语、宾语、介词宾语或表语，既可以指人，也可以指物。
(1)as引导定语从句时，有如下结构：“the same …as”，“such …as”， “as…as”“so many (much, few, little)…as”，译作“像……一样的人(或物)”。例如：
This is such an easy novel as you can read.
这本小说很容易，你能读得懂。
They have never read so many books as I read last year.
他们从来都没有读过像我去年读过的那些书。
(2)as单独引导定语从句时，修饰整个主句或主句中的一部分，可以放在句首、句中或句末。
当as在从句中作主语时，从句的谓语通常是被动语态或系表结构;as在从句中作宾语时，从句的谓语常用“情态动词+动词原形”构成。常见的结构如下：
as is known to all 众所周知
as has been said above 如上所述
as was expected 正如预料的那样
as we all can see (know, hear)正如大家看到的(知道的、听到的)那样。例如：
As is known to everybody, the moon travels round the earth once every month.
众所周知，月球每个月绕地球转一周。
