相對(duì)于主句，定語(yǔ)從句是由關(guān)系詞引導(dǎo)的從句結(jié)構(gòu)。定語(yǔ)從句的主要功能是作名詞修飾語(yǔ)（即“定語(yǔ)”）。
1、限制性定語(yǔ)從句與非限制性定語(yǔ)從句
限制性定語(yǔ)從句和它的先行項(xiàng)有著不可分割的聯(lián)系，缺少了它，作為先行項(xiàng)的名詞（詞組）便不能明確表示其所指的對(duì)象。
Here is the boy who damaged the vase.
非限制性定語(yǔ)從句和它的先行項(xiàng)之間只有比較松散的聯(lián)系，它不是先行項(xiàng)不可缺少的組成部分，而僅僅對(duì)先行項(xiàng)提供一些補(bǔ)充說(shuō)明。因此，如果省略了一個(gè)非限制性定語(yǔ)從句，并不影響先行項(xiàng)所指的意義。
My cousin, who is an engineer, went to Europe last week.
1、限制性定語(yǔ)從句
限制性定語(yǔ)從句在口語(yǔ)中沒(méi)有停頓，在書(shū)寫(xiě)中不用逗號(hào)。
The man who did the robbery has been caught.
The chair (which) I sat in was a broken one.
Can you show me the house where Shakespeare once lived?
當(dāng)名詞中心詞帶有all,any,some,every,no等不定限定詞時(shí)，其后的定語(yǔ)從句也是限制性的。
Any man who smokes cigarettes is risking his health, the doctors says.
Some friends that I made in college were interesting in grades than in learning.
No visitors who come to Beijing would fail to see the Great Wall.
2、非限制性定語(yǔ)從句
非限制性定語(yǔ)從句在口語(yǔ)中有停頓，在書(shū)寫(xiě)中用逗號(hào)隔開(kāi)。
非限制性定語(yǔ)從句的引導(dǎo)詞通常是who,whom,whose 和which等wh-詞，但也并不絕對(duì)排除that。
His speech, which bored everyone, went on and on.
The chairman’s daughter, whose name is Ann, gave me a smile.
關(guān)系副詞when和where也能引導(dǎo)非限制性定語(yǔ)從句（不可以用why引導(dǎo)非限制性定語(yǔ)從句）。
I’m seeing the manager tomorrow, when he will be back from New York.
2、關(guān)系詞的選擇
關(guān)系詞包括關(guān)系代詞、關(guān)系副詞和關(guān)系限定詞（Relative Determiner)，我們主要是講關(guān)系代詞的選擇問(wèn)題。在定語(yǔ)從句中，關(guān)系代詞的選擇受到幾種因素的制約。這首先牽涉到先行項(xiàng)的所指意義，是指人還是指物；也牽涉到關(guān)系代詞在分句中的句法功能，是作分句的主語(yǔ)，還是作賓語(yǔ)或補(bǔ)語(yǔ)；當(dāng)然還要看關(guān)系代詞所引導(dǎo)的從句是限制性定語(yǔ)從句還是非限制性定語(yǔ)從句；同時(shí)還要考慮到定語(yǔ)從句是用于正式場(chǎng)合，還是非正式場(chǎng)合，是用于書(shū)面語(yǔ)，還是用于口語(yǔ)。因此，關(guān)系詞的選擇帶有一定的復(fù)雜性，必須綜合考慮上述諸種因素加以選擇。
1、在限制性定語(yǔ)從句中關(guān)系代詞的選擇
在限制性定語(yǔ)從句中作主語(yǔ)、賓語(yǔ)和介詞補(bǔ)足成分的關(guān)系代詞的選擇問(wèn)題。
1)在限制性定語(yǔ)從句作主語(yǔ)的關(guān)系代詞的選擇，按照一般規(guī)則是用who／that指人，用which／that指物。
He's the man who lives next door to us.
He drives a car that can travel 150 miles an hour.
b)在限制性定語(yǔ)從句中，關(guān)系代詞作賓語(yǔ)，正式語(yǔ)體分別用whom，which指人和指物；非正式語(yǔ)體用who，that指人，用that指物，而且通常省略。
Where is the man whom(=who/that) I saw this morning?
Is that the man whom(=who/that) you gave your tickets to?
Where is the book which(=that) I bought this morning?
Is that the address which(=that) you sent the telegram to?
在上述諸例中，現(xiàn)代英語(yǔ)強(qiáng)烈傾向于用that和zero，除非在非常正式的語(yǔ)體中才用whom／which。
c)關(guān)系代詞作介詞補(bǔ)足成分，在正式語(yǔ)體中介詞通常前置，這時(shí)不管在限制性或非限制性關(guān)系分句中都用whom指人，which指物。
James is a man for whom l have the greatest respect.
在非正式語(yǔ)體中，通常介詞后置，可用who／that指人，that指物，或者都用zero。
They are the boys(who) / (that) I went to school with.
The case (that) you are referring to is now closed.
在介詞后置情況下如果還用whom／which，那就很不自然。
2、在限制性定語(yǔ)從句中關(guān)系代詞的其他用法問(wèn)題
在限制性定語(yǔ)從句中，關(guān)系代詞還有以下用法需加注意：
1）當(dāng)關(guān)系代詞在SVC結(jié)構(gòu)中作主語(yǔ)補(bǔ)語(yǔ)或在there be (存在句）結(jié)構(gòu)中作“實(shí)義主語(yǔ)’時(shí)，通常用that指人或指物，而且通常省略。
The 9:15 is the fastest train (that) there has ever been.
b)在限制性定語(yǔ)從句中，有時(shí)為了明確所指對(duì)象避免歧義，對(duì)關(guān)系代詞的選擇必須慎重。有時(shí)必須用who(m)指人，用which指物，若用that則不恰當(dāng)。
There’s only one student in the school (that) I wanted to see.
There’s only one student in the school whom I wanted to see.更好。
如果先行項(xiàng)既指人又指物的并列名詞詞組，則以用that引導(dǎo)比較合適。
He talked of the man and the books that interested him.
c)當(dāng)先行項(xiàng)為all或其他指物的不定代詞（如anything, something, nothing）時(shí)，關(guān)系代詞作主語(yǔ)通常用that，作賓語(yǔ)用that/zero。
All that live must die.
All (that) I want is peace and quiet.
d)當(dāng)先行項(xiàng)指人并帶有only, all, any等限定詞時(shí)，其后用作定語(yǔ)從句主語(yǔ)的關(guān)系代詞通常用that。
Any boy that wants to succeed must work hard.
Ask Mr Green, or any other person that is likely to know.
e) 當(dāng)先行項(xiàng)帶有最高級(jí)修飾語(yǔ)時(shí)，其后的關(guān)系代詞通常用that。
Newton was one of the greatest men that ever lived.
He’s the cleverest man that ever taught in our school.
3、在非限制性定語(yǔ)從句中關(guān)系代詞的選擇
在非限制性定語(yǔ)從句中，通常用who(m)/whose指人，用which指物。
The driver, who was very young, had just got his licence.
The book, which only appeared a years ago, has already gone through several edition.
在非限制性定語(yǔ)從句中，which的先行項(xiàng)還可以是上文的整個(gè)分句。
He tried to stand on his hands for five minutes, which is rather a difficult thing to do.
4、關(guān)系詞的省略問(wèn)題
引導(dǎo)限制性定語(yǔ)從句的關(guān)系詞在下列場(chǎng)合可以省略。
1)當(dāng)關(guān)系代詞在從句中作賓語(yǔ)時(shí)：
The table you just saw is made of plastics.
Tom is not the boy I gave the tickets to.
The stranger I spoke of came again.
b)當(dāng)關(guān)系代詞that在從句中作補(bǔ)語(yǔ)時(shí)：
He's changed. He's not the man he was.
It's a puzzle to me what has made him the man he is.
c) 當(dāng)關(guān)系代詞在從句中作主語(yǔ)時(shí)，只有當(dāng)主句是由it is，that is, there is引導(dǎo)的場(chǎng)合才能省略。
It isn't everybody can learn a foreign language so easily.
That was his brother just went by.
There was someone asked for you, Bill.
上述省略現(xiàn)象通常只見(jiàn)于非正式語(yǔ)體，但在下列結(jié)構(gòu)中，關(guān)系代詞的省略并不限于非正式語(yǔ)體：
This is the fastest train there is to Beijing.
He asks for the latest book there is on the subject.
d) 三個(gè)關(guān)系副詞when, where, why 可以在the time when，the place where，the reason why結(jié)構(gòu)中引導(dǎo)限制性定語(yǔ)從句，這通常用于正式語(yǔ)體；在非正式語(yǔ)體中，通?？梢允÷躁P(guān)系副詞when和why:
I shall never forget the day (when) we first met.
I remember the morning (when) he first came to school.
The reason (why) he came so early is his own affair.
也可用介詞后置的方法代替where:
The room he worked in is now kept in good repair.
Do you happen to know anybody in the university this dictionary was compiled at?
如果where的先行項(xiàng)是place一詞，那么關(guān)系分句的句末介詞也可省略:
That's the place he stayed when he was in London.
上述用法也適用于表示方式的the way結(jié)構(gòu)。在正式語(yǔ)體中，以the way 作先行項(xiàng)的限制性定語(yǔ)從句通常由in which 或者that 引導(dǎo)。
The way in which you answered the questions was admirable.
但在非正式語(yǔ)體中，通常說(shuō)：
The way you answered the questions was admirable. 未完待續(xù)……