定语从句
用来说明主句中*一名词或代词〔有时也可说明整个主句或主句中一局部〕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, much, 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局部概念。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 petition, 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*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;假设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"
Where:对于关系副词where的考察,趋于一种"地点的模糊化。领先行词表示*人/物的situation,或*事开展的stage,或表达*事的*个方面时都可用关系副词where。常见的先行词还有point,case等。   
3."介词+关系代词"是一个普遍使用的构造
    (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"构造中的介词可以是 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 。
in which =where      for which =why      on which = when
    (2) from where为"介词+关系副词"构造,但也可以引导定语从句。限制性从句例如:
    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
    1.二者差异比拟
    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as is known众所周知,as is often the case情况常常如此,as is supposed如所料想的,as often happens这种情况常常发生,as is e*pected在意料之中例如:
    (1) As is e*pected, the England team won the football match.
  (2) The earth runs around the sun, as is known by everyone.
众所周知, 定语从句可以分为限制性定语从句和非限制性定语从句。下面结合考例谈谈学习运用非限制性定语从句时应注意的几个问题:
  一、that不能用来引导非限制性定语从句。如:
  【考例一】She heard the terrible noise, ________brought her heart into her mouth.
  A. it B. which C. this D. that
  【解析】选B。后半句为非限制性定语从句,尽管先行词noise属于事物,也不能用that而要用which来引导。which指代noise,在从句中作主语。
  二、除which外,还可用when,where,whose,whom等引导非限制性定语从句,且各自的用法及差异与它们用在限制性定语从句时一样。如:
  Ne*t month, when you'll spend your summer holidays in your hometown, is approaching. 下个月即将降临,届时你们将在家乡度暑假。(关系副词when指代表示时间的名词ne*t mont
h,并作从句的状语。)
  She is going to live in Macao, where she has some close friends. 她要到澳门去居住,在那里她有几个密友。 (关系副词where指代表示地点的名词Macao,并在从句中作状语。)
  【考例二】Recently I bought an ancient Chinese vase, ________was very reasonable.
  A. which price
  B. the price of which
  C. its price
  D. the price of whose
  【解析】选B。whose在从句中作表示所属关系的定语,既可指代人,也可指代物。指物时,常可转换为of which;指人时常可转换为of whom。