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高中英语语法重点难点回顾――定语从句
用来说明主句中某一名词或代词（有时也可说明整个主句或主句中一部分）而起定语作用的句子叫作定语从句。
一．词引导的定语从句
1. 关系代词用来指代先行词是人或物的名词或代词
句子成分 用于限制从句或非限制性从句 只用于限制性从句
代替人 代替物 代替人或物
主语 Who which that
主语 Whom which that
宾语 Whose(=of whom) whose(=of which)
例１：This is the detective who came from London.
例２：The book which I am reading is written by Tomas Hardy.
例３：The desk whose leg is broken is very old.
例４：This is the room that Shakespeare was born in.
２．关系代词的用法
(1) 如果先行词是all, much, anything, something, nothing, everything, little, none等不定代词，关系代词一般只用that，不用which。例如：
All the people that are present burst into tears.
(2) 如果先等词被形容词最高级以及first, last, any, only, few, mush, no, some, very等词修饰，关系代词常用that,不用which, who，或whom。例如：
(3) 非限制性定语从句中，不能用关系代词that,作宾语用的关系代词也不能省略。例如：
There are about seven million people taking part in the election, most of whom、are well educated.
(4) which还有一种特殊用法，它可以引导从句修饰前面的整个主句，代替主句所表示的整体概念或部分概念。在这种从句中，which可以作主语，也可以作宾语或表语，多数情况下意思是与and this 相似，并可以指人。例如： He succeeded in the competition, which made his parents very happy.
(5) that可指人或物，在从句中作表语，（指人作主语时多用who）仅用于限制性定语从句中。
(6) which可作表语，既可指人，以可指物。指人时，一般指从事某种职业或是有种特征．品性或才能的人。Which引导的定语从句可以限制性的，也可以是非限制性的。
(7) 如果作先作词的集体名词着眼于集体的整体，关系代词用which;若是指集体中的各个成员，则用who。
(8) 先行词有两个，一个指人，一个指物，关系代词应该用that。例如：
The boy and the dog that are in the picture are very lovely.
(9) 如果先行词是anyone, anybody, everyone, everybody, someone, somebody,关系代词应该用 who 或whom，不用 which。例如：
Is there anyone here who will go with you?
３．“介词＋关系代词“是一个普遍使用的结构
(1) “介词＋关系代词“可以引导限制性定语从句，也可以引导非限制性定语从句。“介词＋关系代词“结构中的介词可以是 in, on, about, from, for, with, to at, of, without 等，关系代词只可用whom或 which,不可用 that 。
(2) from where为“介词＋关系副词“结构，但也可以引导定语从句。例如：
We stood at the top of the hill, from where we can see the town..
(3) 像listen to, look at, depend on, pay attention to, take care of等固定短语动词，在定语从句中一般不宜将介词与动词分开。例如：
This is the boy whom she has taken care of.
二．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。
三．限制性定语从句与非限制性定语从句
1．二者差异比较
限制定语从句紧跟先行词，同先行词这间一般不加逗号，仅修饰先行词，可以由关系代词．关系副词或that来引导。非限制性定语从句仅作补充或说明，用逗号与主句隔开，既可修饰先行词，又可修饰整个主句，不可用that引导。
2．关系代词和关系副词的选择依据
(1) 弄清代替先行词的关系词在从句中作什么成分,作状语的应选用关系副词，作主语．宾语或表语的可选用关系代词。
3. 先行词与定语从句隔离
定语从句一般紧跟在先行词之后，但定语从句与先行词之间有时也会插入别的成分，构成先行词与定语从句的隔离。例如：
1) This is the article written by him that Is poke to you about..
2) He was the only person in this country who was invited
四．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.
冠词用法不用愁，巧记两段顺口溜
有些同学总感到冠词难用，尤其是不知或拿不准什么时候要“加冠”，什么时候“免冠”。这里着重介绍一下有关“定冠词的用法”和“不定冠词的几种情况”的两段口诀：
一、定冠词的用法。
特指双熟悉，上文已提及；
世上独无二，序数最高级；
某些专有名，习语及乐器。
以上口诀归纳了用定冠词的一般情况，即：
①特指某些人或物 ②谈话双方都熟悉的人或事 ③上文已经提到的人或事 ④世界上独一无二的事物前 ⑤序数词回形容词最高级前 ⑥某些专有名词前 ⑦一些习惯短语（如：in the day等）中和乐器前（如：play the violin / piano）。
二、不用冠词的集中情况。
下列情况应免冠，代词限定名词前；
专有名词不可数，学科球类三餐饭；
复数名词表泛指，两节星期月份前；
颜色语种和国名，称呼习语及头衔。
以上口诀主要概括了一般应“免冠”的几种情况，即：
①名词前已有作定语用的this、that、some、any、my等限定词。 ②专有名词和不可数名词前。 ③表示学科的（如：maths、Chinese、physics）名词前。 ④球类活动的名词前及三餐总称前。 ⑤复数名词表示泛指（一类人或事）时。 ⑥节日、季节、星期、月份前。 ⑦表示颜色（如：It's red / yellow.）、语种（如：speak English/Japanese）和国家的非全称名词（如：We live in China. They come from America.）。 ⑧在称呼或表示头衔的名词前。 ⑨某些习惯短语中（如：in bed、go to school等）。
情态动词的推测性用法
1. Possibility (may/might/can/could)
a.在疑问句中表示“可能”，须用can而不用may.
b.在肯定陈述句中，用can表示“可能”与用may往往产生含义上的微妙差别：用表示“可能”往往指逻辑上的；用表事实上的。
Mr Reed is in poor health. He can be ill at any time.
Mr Reed looks pale. He may be ill.
c.用can表“可能”，较多地用于否定句和疑问句，could不受此限。
If you don't have a guide, you could lose your way.
It can’t/couldn't be true.
Can/Could the news be true?
d.表过去的“可能”可用“may/might+不定式完成体或不定完成进行体”，也可用“can/could+不定式完成体”。
She may/might have been expressing her true feelings at that moment.
She can't/couldn't have missed the train.
e.用“might/could+不定式完成体”有时可以表本来可能发生但没有发生，或本来可能完成却没有完成的动作。 You might have killed yourself.
I could have reported you.
使用半倒装的几种情况
1 当句首状语为否定词或带有否定意义的词语时
Never have I found him in such a good mood.
No longer these days is it necessary for women to wear veils.
Visit our stores. Nowhere else will you find such magnificent bargains.
2 当句首状语由only+副词/介词词组/状语分句时
Only yesterday did he find out that his watch was missing.
Only through sheer luck did he manage to get some tickets.
Only because there were some cancelled bookings did he get some tickets in the end.
以关联词not only(but also)开头的句子或成分
Not only did he complain about the food, he also refused to pay for it.
3 以关联连词so(…that)开头的句子，在这种结构中，"so+a"是主语补语的前置；"so+ad."是状语的前置 So small was the mark that I could hardly see it.
So quickly did the workmen finish their work that they were given a bonus.
4 当方式状语、频度状语移至句首
Gladly would I pay more if I could get better service by doing so.
Many a time has Mike given me good advice.
定语从句学习容易出错的几方面
1、在定语从句中加了多余的或缺少宾语成分。
Some of the boys I invited the didn't come.
She told the wrongs had been done to her by the boss.
2、 把定语从句的主谓一致问题。
Those who has finished may go now.
3、 当先行词为表示时间、地点的名词时，分不清关系词在定语从句中所作的句子成分。
Is this the school where Mr. White visited last month?
4、 分不清限制性定语从句和非限制性定语从句。
The naughty boy often knocked at the Wangs' door, that made the family unhappy.
5、与强调句混淆。
It was in the afternoon when I saw him in the park.
应该为：
It was in that afternoon that I saw him in the park.
6、 忽视只能用that，不能用which的情况。
We should do all which is useful to the people.
略谈作后置定语的不定式的语态形式
不定式作后置定语的时态和语态形式在一般情况下是不难理解和使用的。例如，下列句子中的不定式都应用主动形式：
The next train to arrive was from Macao. 下一列到站的火车是从澳门开来的。
Do you know anything about her intention to study medicine? 你知道她为什么想学医吗？