第4个回答 2012-08-19
一、定义：
在复合句中，修饰主句中的某一名词或代词的句子（从句）叫定语从句。定语从句所修饰的词叫先行词。定语从句作定语放在先行词的后面。
引导定语从句的词叫关系词，关系词有：关系代词that，which，who(宾格whom, 所有格whose)和关系副词when，where，why。关系代词或关系副词放在先行词和定语从句之间，既起连接作用，同时又作定语从句的一个成分。如：
The girl who is standing on the stage is my sister.
正站在台上的那个女孩是我的妹妹。（关系代词who在句中作主语）
I can’t find the book (that) I bought yesterday.
我找不到我昨天买的那本书。（关系代词that在句中作宾语，可省去）
Madam Curie was a great scientist whose name is known all over the world.
居里夫人是一位全世界闻名的伟大科学家。
二、用法：
（一）关系代词的用法：
（1）that指物，有时也指人，在从句中作主语或宾语。作主语不可省略，作宾语可省略。
which指物，不指人，在从句中作主语或宾语。作主语不可省略，作宾语可省略。如：
His father works in a factory that/ which makes TV set. （作主语，指物）
The coat (that/ which) I put on the desk is black. （作宾语，可省去）
The books (that/ which) they bought were written by me. （作宾语，可省去）
注意：
(一) which与that指物时可互相代替，但that比which更常见，尤其在口语中。但要注意that可用来指人，而which则不能指人。
只能用that不能用which引导的定语从句：
①定语从句所修饰的词，同时又被形容词最高级修饰时，定语从句只能用that引导；
This is the most interesting story (that) I have ever heard.
②定语从句所修饰的词，同时又被序数词修饰时，定语从句只能用that引导；
The children like the second Lesson that is about “The Football March”.
③定语从句所修饰的词，同时又被the only，the very或the same修饰时，
定语从句只能用that引导；
1) It is the only word (that) I know in the passage.
2) This is the same bicycle (that) I lost.
④定语从句修饰的词同时又被不定代词，如：all，any，no，every，little，many或much等修饰时，定语从句只能用that引导；
Here is all the money (that) I have.
⑤定语从句修饰词为everything，something，anything，nothing，all，none，much，little，few等不定代词时，定语从句只能用that引导。但something前有the时，定语从句可由which引出。
Here is something (that) I will tell you.
I want everything (that) I want.
⑥定语从句修饰的词中同时含有“人”和“物”的名词时，定语从句只能用that引导：
I can remember well the persons and some picture (that) I see in the room.
⑦定语从句修饰的词为one, ones时，定语从句用that引导：
Is it the one (that) you want?
⑧当主句的主语是疑问词 who或 which来提问时，为了避免重复，用that引导定语从句：]
Who is the girl that won the first place?
(二) who指人，that除指人外也指物，在从句中作主语或宾语。作宾语可省略，作主语不能省略。
1) The girl who often helps me with my English is from England. （作主语，不可省略）
2) The teacher who spoke at the meeting just now is having a rest in his office. （作主语，不可省略）
3) The boy (who/ that) I like isn’t here now. （作宾语，可省略）
注 意:
who与that指人时可互相代替，但下列情况只能用who不能用that引导的定语从句：
① 先行词是one，ones，anyone时，定语从句只能用who引导；
② 先行词为those时，定语从句只能用who引导；
③ There be句型开头。
另 注：(1) whom指人，为who的宾格形式,在句中只作宾语，其前没有介词时，也可用who替换使用，也可省略，如：
Who is the teacher (that/ who/ whom) Yanzhen is talking to? （作宾语，可省略）
Who is the teacher to whom Yanzhen is talking? （作宾语，介词to提到whom前，whom再此不可省略）
(2) whose 指人，也可指物，在从句中作定语，不可省略。如：
The building whose windows face to the south is our school. （作定语，不可省略