二．定语从句：定语从句三步：第一找出先行词（被修饰的那个名词或代词）；第二看从句缺少什么成份（如主语、宾语或状语）；第三选择合适的引导词。
注意：引导词在介词后，指人只能用whom 指物只能用which高考对定语从句的考查常涉及以下几个方面：【考点6】正确区别限制性定语从句与非限制性定语从句的结构；理解关系代词和关系副词在定语从句中的作用；特别注意指代整个主句内容的关系代词which引导的非限制性定语从句。
非限制性定语从句，从意义上来说，是对主语的补充说明，从结构上来看，先行词和定语从句之间用逗号隔开，He makes great progress in his English learning, which makes his mother very happy.⑧I shall never forget the day _____ Shenzhou V was launched, _____ has a great effect on my life.A. when; whichB. that; whichC. which; thatD. when; that (2004北京东城)【考点7】关系代词that，who，which以及as的用法区别。
指人时常只用who不用that的情况；指物时只用which不用that的情况；只用that不用which的情况；关系代词as与which的用法区别；the same … that … 与the same … as …的区别:1 其中that, who(whom)，都可以指人，那么他们在指人时有什么区别呢。
[本条记忆技巧：用who 不用that 的情况“there be” “one，ones，anyone，nobody, those ” 被分割。
那里有(there)很多万(one)被那些人(those)分割。
]<1>先行词为those, one, anyone, nobody 等词时，用who不用that,例如：The one who knows me well is Tom.<2>在分隔型定语从句中，若先行词是人，用who不用that, 例：A new teacher will come who will teach you German.在本句中，先行词“teacher”和修饰限定它的从句“who will teach you German ”分离，所以我们用who 不用that。
<3>先行词为“there be”结构的主语时，例如There is a man who wants to see you.在本句子当中a man是There is a man 这句当中的主语，所以用who不用that2其中，that 和which 都可以指物，它们在指物时的区别：用that不用which<1>先行词前有形容词最高级,序数词,all, every, little, no, any, much, the only, the very, the last 等修饰时，例如：I have read all the books that you gave me.<2>先行词为all, few, nothing, everything, little, much等不定代词时：He did all that he could do to help us.<3>主语以who或which开头时Who is the man that just called you just now?<4>关系代词在从句中做表语时China is not the country that is was.<5>既指人又指物时He talked about the teachers and schools that he had visited.2, 先行词表示物时, 用which不用that 的情况<1> 引导非限制性定语从句时,例如:She heard a terrible noise, which brought her heart to her mouth.<2>当关系代词做介词宾语时,例如:He wrote a book in which he could learn about his life.在上一例句中,引导词“which”作了介词“in”的宾语,所以不可以用“that”代替.关于as1在一些结构，如“such …as” “the same…as” “as…as”等结构中，定语从句的引导词经常要用到as，例如This is not such a book as I expected.the same as和the same that 的区别。
例句：This is the same tool as I used last time.This is the same tool that I used last time.在例句中，第一句的意思是这个工具和我上次用的一样，但是第二句的意思是这就是我上次用的工具2 as 和which 的比较相同点：两者都可以引导非限制性定语从句，先行词都可以是整个句子，都可以在从句中做主语，宾语表语。
不同点: <1> as 引导的从句可以放在句首和句尾，而which 引导的从句只可放在句尾。
<2>as 还有正如、正象的意思。
As Marx pointed out, labor created man himself.当先行词，虽然表示时间地点，但是引导词在从句中不是做状语，而是做宾语时，不能用when, where引导，而只能用that, which 等引导。
比较以下两个句字：I will never forget the days when I first went to Beijing .I will never forget the days that (which) we spent together⑨ There is no such place ___ you dream of in all this world. (2004北京西城·5月)A. thatB. whatC. whichD. as【考点8】区别that引导的定语从句与that引导的同位语从句。
that引导同位语从句时，that是纯连词，在从句中不充当任何成分；that引导定语从句时，that是关系代词，在从句中充当主语或宾语等。
比较：The news that they had won the game arrived soon.The news that you told me yesterday is true.⑩ Is this the reason _____ at the meeting for his carelessness in his work? (2002上海春季)A. he explainedB. what he explainedC. how he explainedD. why he explained【考点9】定语从句中谓语动词须与先行词在人称与数上保持一致。
⑾ He is the only one of the students who ________ a winner of scholarship in three years.A. isB. areC. have beenD. has been(2002上海春季)【考点10】在先行词为time，place，reason时，常可用that代替when，where，why，并常常省去。
如：That was the reason (that) / why / for which he left home.⑿ What surprised me was not what he said but _______ he said it.(2004湖北)A. the wayB. in the way thatC. in the wayD. the way which【考点11】定语从句应特别注意的几个问题Ⅰ．关系代词which例1．The Greens will move into the new house next Monday, ＿＿＿＿＿it will be completely finished．A．by the time B．by which time C．that D．which例2．Water boils at 100℃, ＿＿＿＿＿it changes to gas．A．at which temperature B．at which C．by which temperature D．by which析：which 引导定语从句时，在从句中除了作主语或宾语外，还可以作定语修饰名词，常用于“介词＋which＋名词”结构中，相当于“and＋介词＋this／that＋名词”。
所以例1选B；例2选A。
Ⅱ．关系副词when例1．Could you suggest a time ＿＿＿＿＿it would fit you to visit us and try out the machine﹖例2．Think of a time ＿＿＿＿＿you were happiest．(Senior3,L93)例3．There was a time ＿＿＿＿＿all scientists were willing to share their results．（Senior3,L3）A．that B．when C．which D．where析：当先行词为a time(一段时间)时，引导定语从句的关系词常用when，而不采用that，故以上例题均选B。
在我们课本中类似的句子还有：①This was at a time when there was no radio, TV or cinema．(Senior2,L70) ②It’s about a time when there were black slaves in North America．(Senior1,L53)Ⅲ．关系代词but例：There is no one ＿＿＿＿＿wishes peace．A．who B．but C．that D．whom析：本题句意为“没有人不希望和平。
”but作关系代词，在定语从句中作主语。
but相当于who ／th at don’t ／doesn’t，but本身含有否定意义。