关系代词的概念：

英语中的关系代词有who, whom, whose, that, which, 它们是用来引导定语从句的。关系代词既代表定语从句所修饰的词，又在其所引导的从句中承担一个成分，如主语、宾语、表语、或定语。
如：This is the man who saved your son. (who在从句中作主语，先行词是man） 
        The man whom I met yesterday is Jim.
        A child whose parents are dead is an orphan.
        He wants a room whose window looks out over the sea.

关系代词用法：

1、that与which的用法区别：
      两者都可指物，常可互换。其区别主要在于：
（1）引导非限制性定语从句时，通常要用which：
如：She received an invitation from her boss, which came as a surprise. 她收到了老板的邀请，这是她意想不到的。
（2）直接放在介词后作宾语时，通常要用which：
如：The tool with which he is working is called a hammer. 他干活用的那个工具叫做锤子。
（3）当先行词是下列不定代词或被它们修饰时much, little, none, all, few, every(thing), any(thing), no(thing)等时，通常用that：
如：There was little that the enemy could do but surrender. 敌人无法,只有投降了。
        All[Everything] that can be done must be done. 凡能做的事都必须做。
（4）当先行词有the very, the only, the same等修饰时，通常用that：
如：This is the only example that I know. 我知道的例子只有这一个。
        Those are the very words that he used. 那是他的原话。
（5）当先行词有形容词最高级或序数词（包括last, next等）等修饰时，通常用that：
如：This is the best dictionary that I've ever used. 这是我用过的最好的词典。
        The first thing that you should do is to work out a plan. 你应该做的第一件事是订个计划。 
（6）当关系代词在定语从句中用作表语时，通常用that：
如：China is not the country(that) it was. 中国已不是过去的中国了。
（7）当先行词是一个既指人又指物的并列词组时，通常用that：
如：They talked about the persons and things that most impressed them. 他们谈论了使他们印象最深的人和事。
（8）当要避免重复时：
如：Which is the course that we are to take? 我们选哪门课程？

2、that与who的用法区别：
（1）两者均可指人，有时可互换：
如：All that[who] heard him were delighted. 所有听了他讲话的人都很高兴。    
        Have you met anybody that[who] has been to Paris? 你遇见过到过巴黎的人吗?
        He is the only one among us that[who] knows Russian. 他是我们中间唯一懂俄语的人。
（2）但是在下列情况，通常要用that： 
   ①当先行词是一个既指人又指物的并列词组时： 
如：I made a speech on the men and things that I had seen abroad. 我就我在国外所见到的人和事作了报告。
   ②当先行词是who时(为避免重复)：
如：Who was it that won the World Cup in1982? 谁赢得了1982年的世界杯？
   ③当关系代词在定语从句中作表语时(可省略)：
如：Tom is not the boy(that) he was. 汤姆这孩子已不是以前那个样子了。

关系代词知识体系：

关系代词用法拓展：

1、as与which的用法区别：
(1)引导限制性定语从句时，在such,as,thesame后只能用as，其他情况用which：
如：I never heard such stories as he tells. 我从未听过他讲那样的故事。
        It's the same story as I heard yesterday. 这故事跟我昨天听到的一样。
        This is the photo which shows my house. 这张照片拍的是我的住宅。
(2)引导非限制性定语从句时，有时两者可互换：
如：I live a long way from work, as [which] you know. 我住得离工作单位很远，这你是知道的。
(3)但在，在以下情况引导非限制性定语从句时，两者不可换用：
①当从句位于主句前面时，只用as：
如：As is known to everybody, the moon travels round the earth once every month. 月球每月绕地球转一周，这是每个人都清楚的。
②as引导的非限制性定语从句应与主句在意义上和谐一致，which无此限制：
如：He went abroad, as[which] was expected. 他出国了，这是大家预料到的。
        He went abroad, which was unexpected. 他出国了，这让大家感到很意外。(不用as)
③as引导非限制性定语从句时，先行词通常不能是主句中某个具体的词，而应是整个句子、整个短语或某个短语推断出来的概念，而which则无此限制：
如：The river, which flows through London, is called the Thames. 这条流经伦敦的河叫泰晤士河。(不用as)
④当as引导非限制性定语从句作主语时，其谓语通常应是连系动词，而不宜是其他动词，而which则无此限制：
如：She has married again, as[which] seemed natural. 她又结婚了，这似乎很自常。
        She has married again, which delighted us.她又结婚了，这使我们很高兴。(不用as)

2、who与whom的用法区别：
两者均只用于人，从理论上说，who为主格，whom为宾格：
如：Where's the girl who sells the tickets? 卖票的女孩在哪里？
        The author whom you criticized in your view has written a letter in reply. 你在评论中批评的那个作者已写了一封回信。
但实际上，除非在正式文体中，宾格关系代词whom往往省略不用，或用who或that代之：
如：The man(that, who, whom) you met just now is called Jim. 你刚遇见的那个人叫吉姆。
不过，在以下几种情况值得注意：
(1)直接跟在介词后面作宾语时，只能用whom，而且不能省略：
如：She brought with her three friends, none of whom I had ever met before. 她带了3个朋友来，我以前都没见过。
(2)引导非限制性定语从句且作宾语时，who和whom均可用，但以用whom为佳，此时也不能省略：
如：This is Jack, who[whom] you haven't met before. 这是杰克，你以前没见过。

非限制性定语从句的概念：

非限制性定语是对被修饰名词或代词的附加说明，它不是必需的，如果去掉，也不会影响句子的意思，它与被修饰名词之间通常用逗号分开。
如：The travellers, knowing about the floods, took another road. 游客们知道发了大水，都改道走了。
        The boys, wanting to play football, were disappointed when it rained. 那些男孩子想踢足球，因为下雨感到失望。

非限制性定语从句用法：

1、引导非限定性定语从句时，只能用which(不用that)。
例如：Heat is another form of energy, which is as important as other kinds of energy.
            热是另一种形式的能量，与其他形式的能量一样重要。 （从句表补充说明，而且关系代词which不能换成that。） 　　
2、引导非限定性定语从句的which可以指代前面的先行词,也可以指前面整个句子的含义。
例如：That Peter will marry Alice, which has not been announced yet, has spread around.
            彼特要娶爱丽斯这件事还没宣布，却已传得沸沸扬扬。（句子中的which指“彼特要娶爱丽斯”这整个句子的意思。） 　　
3、除which外，还可用when，where，who等关系代、副词引导非限定性定语从句。
例如：After graduation, I decided to stay in Chongqing, where I spent my childhood and four years of college life. 
毕业后，我决定留在重庆，在那里我曾度过了我的童年和四年大学生活。 　　                 
Albert Einstein left Germany for the United States during World WarII, when Jews were badly treated in Germany.  
第二次世界大战期间，爱因斯坦离开德国去了美国，那时犹太人在德国受到不好的对待。 　　
4、在限定性定语从句中作宾语时，引导词可以省略，但引导非限定性定语从句的关联词不能省。
如：He was eager to go to the hospital to see his stepmother, whom he loved and respected as his own mother. 
他急于想去医院看望他的继母，他把他的继母当作亲生母亲一样热爱和尊敬。 　　    
The American journalist(whom/who) the announcer mentioned in the news broadcast is said to have been killed by the gangsters.
 播音员在新闻广播中提到的那位美国记者据说已经被匪徒杀害了。 　　
两例中的关系代词都在从句中作宾语。由于第二例是限定性定语从句，可以省略关系代词；第一例中的引导词不能省略，因为它引导的是非限定性定语从句。 　　
5、表示“正如”的含义时，通常用as引导非限定性定语从句，也可用which引导；但置于句首时，只能用as引导。 　　
如：China has basically succeeded in defeating SARS, which/as we have expected.
        正如我们所预料的那样，中国已基本上战胜了“非典”。 　　  
        As is well known to everybody, Tai wan is an inseparable part of China.
        众所周知，台湾是中国不可分割的一部分。 　　
但是当非限定性定语从句是否定含义时，就只能用which(而不用as)引导。
如：He didn't win the championship, which I hadn't expected.
        他没获得冠军，这一点是我没预料到的。

非限制性定语丛句中as, which的区别：

1、which引导非限制性定语丛句代表前面的整个句子的时候，一般是对主句的结果的说明。 
      如： He grows too fast, which makes him taller than his classmates.
2、as引导非限制性丛句代表前面整个句子时一般来讲丛句的谓语动词有三种：
A. 含有be动词：
如：He failed the exam, as is natural.
B. 实意动词的被动形式：
如：As is reported, the fire caused a great loss.
C.感官动词和意识类动词如：
如：see, hear, notice, know, learn, realize 等。 
        As you know, I am a teacher.
3、as可翻译为正如，它引导的丛句可位于主句之前，也可位于主句之后；which引导的该丛句只能位于主句之后。
例1：__A___he realized, I was very useful to him. 
例2：This elephant is like a snake, ___A__anybody can see. 
例3：The sun gives us light and heat, __B___makes the plan tgrow well.
          A. As(as)
          B. which
          C. that
          D. who

限定性定语从句与非限定性定语从句的区别：

非限制性定语从句的关系词：

非限定性定语从句的使用规则及注意事项：

1、which引导的非限定性定语从句是用来说明前面整个句子的情况或主句的某一部分。
2、在引导限定性定语从句时，that有时相当于in which, at which, for which或at which。其中，介词的选用，依据从句中的动词所需搭配的介词来选用。例句：
① Attitudes towards day dreaming are changing in much the same way that(inwhich)attitudes towards night dreaming have changed.
    人们对白日做梦的态度正在改变，这与人们对夜间做梦的看法的变化有非常相似之处。
② I like the music for the very reason that(for which) he dislike it. 
    我出于某种原因喜欢这种音乐，而他恰恰与我相反。
③ We arrived the day that(on which) they left.
    刚好我们到的那天他们走了。
3、as有时也可用作关系代词。
4、在非限定性定语从句中，关系词不能用that。

强调句的概念：

强调句 (The Emphatic Pattern) 是一种修辞，是人们为了表达自己的意愿或情感而使用的一种形式。通过各种方式对句子中的某个部分进行强调，从而起到修辞的作用。英语常用的强调结构有：It is (was)+被强调部分(主语、宾语或状语)+that/who...；what…be…句型；

强调句的使用:

一、强调句句型：
1、用It is／was...that／who...句型表示强调。
（1）陈述句的强调句型：It is/was+被强调部分（通常是主语、宾语或状语）+that/who（当强调主语且主语指人）+其它部分。
e.g. It was yesterday that he met Li Ping.
（2）一般疑问句的强调句型：同上，只是把is/was提到it前面。
e.g. Was it yesterday that he met Li Ping?
（3）特殊疑问句的强调句型：被强调部分（通常是疑问代词或疑问副词）+is/was+it+that/who+其它部分？
e.g. When and where was it that you were born?
注：被强调的部分（通常是句子的主语、状语、宾语或宾语补足语）放在is／was的后面，如被强调的是人，则后面可用who，whom等代替。
如：原句：He met an old friend in the park yesterday.  
        强调主语：It was he who/that met an old friend in the park yesterday.
        强调宾语：It was an old friend that/who he met in the park yesterday. 
        强调地点状语：It was in the park that he met an old friend yesterday. 
        强调时间状语：It was yesterday that he met an old friend in the park.
2、用助动词do, does或did来强调谓语动词。
如：Do come early. 
        He did send you a letter last week.
        We're pleased that she does intend to come.
3、用主语从句+be+被强调部分，主语从句常用what引导。
如：What John wants is a ball.
        What Mary does every day is(to) give piano lessons.  

二、not...until...句型的强调句：
1、句型为：It is/was not until+被强调部分+that+其它部分：
e.g. 普通句：He didn't go to bed until/till his wife came back. 
       强调句：It was not until his wife came back that he went to bed.
2、注意：此句型只用until，不用till。但如果不是强调句型，till, until可通用；
因为句型中It is/was not...已经是否定句了，that后面的从句要用肯定句，切勿再用否定句了。

三、谓语动词的强调：
1、It is/was...that...结构不能强调谓语，如果需要强调谓语时，用助动词do/does或did。
e.g. Do sit down.务必请坐。
      He did write to you last week. 上周他确实给你写了信。
      Do be careful when you cross the street. 过马路时，务必（千万）要小心啊！
2、注意：此种强调只用do/does和did，没有别的形式；过去时用did，后面的谓语动词用原形。 

使用强调句型有以下几点请注意：

①强调句的谓语is或was永远用单数。
如：It was yesterday that I met your father in the street.
②不管被强调部分是哪种状语，只能用that连接，不得使用where、when等连词。
如：It was in the street that I met your father yesterday.
③被强调部分为人时，可用who(主格或宾格)和whom(宾格)代替that，用that也行。
如：It was your father that/whom/who I met in the street yesterday.
        It was I that/who met your father in the street yesterday.
④强调句中也要注意主谓一致、人称一致和否定转移的问题。
如：It is they who are our friends.
        It was not until ten o'clock that we got home last night.
⑤注意不要混淆强调句和其他从句。It is/was...that...为强调句标志，去掉后仍可组成一个完整的句子，只是没被强调，而其他从句一般不具备这一特征。
比较：1）It was ten o'clock when we got home last night. 我们昨晚到家时已十点了。
            2）It was at ten o'clock that we got home last night. 我们昨晚是在十点到家的。
第一句不是强调句，when不可改为that，因为去掉it was和that后，只能组成“We got home ten o'clock last night.”这样一个不完整的句子；第二句是强调句，that不可改为when。

强调句型用法拓展：

1、句首词用“It”，不能用“This”，“That”等。
2、be动词的形式是is或was，不能用复数形式are或were。若原句的谓语动词用了现在时或将来时，则用is；
若原句的谓语动词用了过去时或过去完成时，则用was。
如：It___the Chinese women that___a great role in the socialist construction.
A. is; plays
B. are; play
C .is; play
D. are; plays
答案：C 
3、被强调的部分如果是代词，强调主语用主格，强调宾语用宾格。
如：It is him that/who/whom I met in the street yesterday.
        It is I who/that am wrong.
4、连接词一般用that，当强调部分是人时，既可用that也可用who。特别注意当强调部分是时间状语或地点状语时，不能用when或where。
如：It was on Oct1st, 1949 that People's Republic of China was founded.
        It was at the gate____he told me the news.　　
        A. that
        B. what
        C. which
        D. when
答案：A
5、主谓一致问题被强调的主语要和that后面的谓语动词在数上保持一致。
如：It is Mary who often _____(help) me with my English. （helps）
        It is I that ____(be) against you. （am）
6、not...until结构的强调。
强调“not...until”引导的时间状语时，要用“it is/was not until...that...”结构，that后面的句子要用肯定式，且须用陈述句语序。 
如：We did not get off the bus until it stopped. ?
        It was not until it stopped that we got off the bus. (注意：强调该结构时not until不能分开)