定语从句

1.综述

定语从句也称为关系从句或形容词性从句，由关系代词（who, whom, whose, which, that, as ）或关系副词（when, where, why）等引导。关系词除了起引导作用外，还在从句中指代前面的先行词，并在从句中担任一定的成分。如：

The car which was stolen has been found.（which 指代先行词car，在从句中作主语）

The house whose windows are broken is empty. (whose 是所有格，在从句中作定语)

I shall never forget the day when I entered the university. (when指代先行词day，在从句中作时间状语)

2.限定性定语从句和非限定性定语从句

1）定语从句就其与先行词的关系而言，可分为限定性定语从句和非限定性定语从句。限定性定语从句和先行词之间没有逗号，表示对先行词起修饰限制作用；而非限定性定语从句和先行词之间有逗号分开，是对先行词进行补充说明，相当于并列句。如：

   He is the man who has a strong personality. 他是个个性很强的人。（限定性定语从句）

   My brother, who works abroad, is coming next week. 我哥哥在国外工作，他下周将回来。（非限定性定语从句）

   注：1. 非限定性定语从句不能用that来引导，一般用which，as或who（指人）。用which或as引导时，既可以修饰主句的部分内容，也可修饰主句的全部内容。如：

    He spoke confidently, which impressed me most. （which指代整个主句，在从句中作主语）

2） as引导的非限定性定语从句既可以放在主句之前，也可以放在主句之后，但which或who引导的非限定性定语从句不能放在主句之前。如：
As we all know, the moon is a satellite of the earth.
The large area is covered with thick snow, which affects  people‘s   life greatly.

3）在限定性定语从句中，关系代词作宾语时可以省略；但在 非限定性定语从句中，关系代词作宾语时不能省略。如：

     The film (which) I saw last night is about a young teacher.   (which可以省去)

     She introduced me to her husband, whom I hadn’t met before.  (whom不能省去)

3.只用关系代词that，不用 which，who或whom的几种情况

A．当先行词是all, everything, nothing, something, anything,  little, much, none, few等时。如：
All that you want are here.

B．当先行词被all, no, some, any, every, a few, a little, much, only, very等修饰时。如：

    There is no person that doesn’t make mistakes.  

C． 当先行词被序数词或形容词最高级修饰时。如：

This is the best film that I have ever seen.

D．当出现两个或两个以上的先行词，并同时兼指人和物时。如：
    We are talking about the people and countries that we have visited.

E．当主句是以which 或 who 开头的特殊疑问句时。如：
     Who is the person that is standing over there?

F．当定语从句为there be 句型时，关系代词只能用that， 但经常可以省略。如：
    I know the difference (that) there is between you.

G．当关系代词在从句中作表语时，常用that。如：

    He does not seem to be the man that he was.

    他似乎和过去不一样了。

4. as 与其他词连用引导的定语从句

as 引导定语从句时，可指人也可指物，通常与the same，such，so等连用，形式为：the same… as，such… as，as …as，so… as。As在定语从句中可作主语、宾语、表语等。如：

She knew he felt just the same as she did.  她知道他的感觉与她自己的一样。(as代替事，作宾语)

I lend you such books as will interest you. 我借给你使你感兴趣的书。(as代替物，作主语)

注：the same… as 和the same… that的用法不同。as引导的定语从句表示其内容与主句所讲的事物“相似”，指同类事物；that引导的定语从句表示其内容与主句所讲的事物是“同一个”，指同一事物。如：

This is the same pen as I lost yesterday. 这和我昨天丢的笔一样。（类似的笔）

This is the same pen that I lost yesterday. 这支笔就是我昨天丢的那支。（同一支笔）

5. “介词+关系代词”引导的定语从句

在“介词+which/whom”结构中，介词的选择取决于3种情况：

A．定语从句中谓语动词或表语的搭配。如：
     This is the college in which I am studying.
     He is the man about whom we are talking.
  B. 先行词与介词的习惯搭配。如：
     The speed at which the machine operates is shown on the meter. 仪表上显示出这台机器运转的速度。
  C. 当定语从句为最高级时只能用of which; 否则用其他介词。如：
   I have five dictionaries of which Longman Dictionary is the best.
   I have five dictionaries among which Longman Dictionary is published in UK.

注：不可拆分的动词短语介词不能提前，如put up with；有的短语可能有不同的介词搭配，此时需要根据上下文来确定。如：be familiar with/to，compare with/to等有时为表意清楚，还可以在关系副词where/ when前加介词from, to等。如：

China is the birthplace of kites, from where kite flying spreads to Japan, Korea, Thailand and India.

中国是风筝的故乡，从这里，放风筝的运动传到了日本、韩国、泰国和印度。

6. 定语从句和同位语从句的区别

定语从句在复合句中的功能相当于形容词，它对先行词起修饰、描述或限制作用。而同位语从句则属于名词性从句，对与它有同位关系得名词作进一步解释，使其内容具体化。例如：

She felt very sad because of the news that her husband was killed in an aircraft crash. (同位语从句)  

The fact that she told me made me very angry. （定语从句）

状语从句

状语从句就是充当句子状语的从句，它可分为时间、地点、方式、比较、原因、结果、目的、条件和让步等从句。

时间状语从句 

1.常用来引导时间状语从句的连接词有as, when, whenever, while, before, after, till, until, since, as soon as, hardly/scarcely/barely…when/before…, no sooner… than…等。如：

     He made a mistake，but then he corrected the situation before it got worse．

     他犯了错误，但没等局势恶化，他就扭转了局势。

     Jack had scarcely/hardly seen me when/before he left the room. 杰克一看到我就离开了房间。

2．某些表示时间的副词、名词短语和介词短语也可引导时间状语从句。如directly, immediately, the instant, the moment, the minute, the day, the year, each/every time, next time, the first/second/last time, by the time等。 如：

     Directly I received your letter, I came back at once. 我一收到你的信，就马上回来了。

 地点状语从句

地点状语从句一般由where, wherever, everywhere 和anywhere引导。如：

Wherever he went, he was warmly welcome. 无论他走到哪里，都受到热烈的欢迎。

原因状语从句

原因状语从句一般由because, as, since, now that, in that, seeing that, considering that, not that… but that, by reason that, for fear that, for the reason that, on the ground that等引导。 如：

As it is raining, let’s stay at home. 因为下雨，我们就留在家里吧。

A gas differs from liquid in that it has no definite shape. 气体不同于固体就在于它没有一定的形状。

结果状语从句

结果状语从句由so… that, such… that, so that, such that, so, that, to such a degree that, to such an extent that, with the result that等引导。

The shock was such that she was almost driven mad. 因为打击太大，她差点发疯。

The temperature rose to such an extent that the firemen had to leave the house. 

温度如此之高，消防队员不得不离开那个着火的房子。

注：so 或such位于句首时，主句需用倒装语序。如：

So fierce was their dog that no one dared come near. 他们的狗真凶恶，没有人敢走近它。

目的状语从句

目的状语从句常由that, so that, in order that, lest, for fear that, in case等引导。从句谓语常由“can/could, may/might＋动词原形”构成，有时也用“shall/should，will/would ＋动词原形”。 如：

We left early so that we could catch the first train. 我们很早出发，以便能赶上第一班火车。

He ran away lest he (should) be caught. 他怕被抓，因而逃走了。

条件状语从句

条件状语从句由if, unless, only if（只要）, if only（但愿），when（如果），suppose/supposing（假如），as/so long as（只要），given that（假设），provided/providing that（假如），granted/ granting (that)（假定），on condition that（条件是……）等引导。如：

    I’ll lend it to you as long as you handle it with care. 只要你小心使用，我会借给你的。

注：若主句为一般将来时，条件状语从句中谓语需用一般现在时代替将来时。如：

    If you are free tomorrow, I will go to see you. 如果你明天有空我就去看你。

但如果从句表示的是主语的意志、志愿或以you作主语表示请求时，则用will，would。如：

    I’d be very glad if you would come. 如果你肯来我会非常高兴。

让步状语从句

让步状语从句由as, though, although, even if/though, whatever, whoever, whichever, however, whether… or…, no matter+ wh-词, be, while, granted that, for all that等引导。如：

     While/Although he has some shortcomings, he also has some good points.

虽然他有一些缺点，但也有一些优点。

     Everybody must obey the law, be he a common citizen or a high rank official.   

人人都应该守法，不管他是平民百姓，还是高官

注：as 和though引导的让步状语从句通常用倒装结构，as必须用倒装结构，though可用也可不用倒装。这种倒装通常是把从句中的表语、状语或谓语动词放在句首。如：

     Selfish as/though he is, he is not without merits. 尽管他自私，但不是没有优点。

 方式状语从句

方式状语从句由as, as if/though, the way, how, as… as, not so/as… as, just as (…so)等引导。 如：

It looks as if/as though it is going to rain.看上去要下雨了。

Do it the way (that) you were told. 要照告诉你的去做。

 比较状语从句

引导比较状语从句的连词有：as…as, not so…as, not as…as, the …the…, than等。例如：

I haven’t done as much as I should have expected.我做的没有我希望的那么好。

She knows more than I did at her age.她知道的东西比我在她这个年龄时知道的要多。