关系代词that 的用法(1)不用that的情况(a) 在引导非限定性定语从句时。
(错)The tree, that is four hundred years old, Is very famous here.(b) 介词后不能用。
We depend on the land from whic h we get our food.We depend on the land that/whic h we get our food from.(2) 只能用that作为定语从句的关系代词的情况(a)在there be 句型中，只用that，不用which。
(b)在不定代词，如：anything, nothing, the one, all等作先行词时，只用that，不用whic h。
(c)先行词有the only, the very,the same,the last,just修饰时，只用that。
(d)先行词为序数词、数词、形容词最高级时，只用that,不能用whic h。
.(e)先行词既有人，又有物时。
(f) 先行词指物，在主句中作表语时．(g) 为了避免重复．(h)先行词是the way或the reason时，that可作关系副词，也可省略(i) 主句的主语是疑问词who /which时举例：Is this the book that you borrowed in the library?这是你在图书馆借的那本书吗？Who that break the w indow should be punished．谁打碎了窗户都要受到惩罚．All that is needed is a supply of oil.所需的只是供油问题。
Finally, the thief handed everything that he had stolen to the polic e.那贼最终把偷的全部东西交给了警察。
that必用1先行词是最高级或被最高级修饰2是序数词或被序数词修饰3不定代词4先行词即指人又指物5被only；the every，no，one of等修饰6主句有which；w ho；whom7there be 句型中8如果有两个从句，其中一个关系代词已用了whic h,另一个关系代词宜用that 9先行词在主句中作表语，或者关系代词本身作从句的表语是宜用thatthat在作宾语时可省难点分析（一）限制性定语从句只能用that的几种情况1、当先行词是anything, everything, nothing (something 除外), few, all, none, little, some等代词时，或者是由every, any, all, some, no, little, few, much，each等修饰时(1) Have you taken down everything (that) Mr. Li has said?(2) There seems to be nothing (that) seems impossible for him in the world.(3) All that can be done has been done.(4) There is little (that) I can do for you.注意1：部分时候that可以省略，如部分例句将that用括号括住。
注意2：当先行词指人时，偶尔也可以用who(4) Any man that/.who has a sense of duty won’t do such a thing.2、当先行词被序数词修饰The first plac e that they visited in London w as the Big Ben.3、当先行词被形容词最高级修饰时This is the best film that I have seen.4、当形容词被the very, the only，the same,the last 修饰时(1) This is the very good dic tionary that I w ant to buy,(2) After the fire in his house, the old c ar is the only thing that he owned.当先行词指人时，偶尔也可以用who(3) Wang Hua is the only person in our school who w ill attend the meeting？5、当先行词前面有who, whic h等疑问代词时(1) Who is the man that is standing there?(2) Which is the T-shirt that fits me most?6、当先行词既有人，也有动物或者物体时Can you remember the sc ientist and his theory that we have learned?7.当关系代词在定语从句中做表语The village is no longer the one that it used to be 10 years ago.8.当在there be句型中，通常情况下用that，不用whic h（二）关系代词as和which引导的定语从句as和whic h引导非限制性定语从句，有相同之处也有不同之处。
具体情况是：1、As和whic h都可以在定语从句中做主语或者宾语，代表前面整个句子。
(1) He married her, as/which was natural.(2) He was honest, as/whic h we c an see.2、as 引导非限制性定语从句，可放在主句之前，或者主句之后，甚至可以切割一个主句；which引导的非限制性定语从句只能放在主句之后。
另外，as有“正如……，正像……”的意思(1) As is known to all, China is a developing country.(2) He is from the south, as we c an see from his accent.(3) John, as you know, is a famous writer.(4) He has been to Paris more than several times, whic h I don’t believe.注意：当主句和从句存在逻辑上的因果关系时，常用which。
(5) Tom w as always late for school, whic h made his teac her angry.3、当先行词受suc h, the same修饰时，常用as(1) I have never heard such a story as he tells.(2) He is not such a fool as he looks.(3) This is the same book as I lost last week.注意：当先行词由the same修饰时，偶尔也用that引导定语从句，但是和由as 所引导的定语从句意思不同(4) She wore the same dress that she wore at Mary’s wedding.她穿着她在MARY婚礼上穿过的一条裙子。
(5) She wore the same dress as her young sister wore. 她穿着和她妹妹所穿的一样的裙子。
注意：定语从句such…as …与结果状语从句such… that…的区别：as在所引导的定语从句中作主语，宾语；that在结果状语从句中不做成分(6)He has suc h a good laptop as I want to buy.(7)He has suc h a good laptop that I w ant to buy one.(三）以the way为先行词的定语从句通常由in whic h, that引导，而且通常可以省略。
The way in which/ that/./ he answered the question was surprising.(四) but有时也可以做关系词引导定语从句There are very few but understand his idea。
( but= who don’t )(五) 区分定语从句和同位语从句1、定语从句修饰先行词，它和先行词是修饰关系；同位语从句说明先行词的具体内容，是补充说明的关系(1) The plane that has just taken off is for London. 定语从句(2) The fac t that he has been dead is c lear. 同位语从句2、定语从句由关系代词或者关系副词引导，关系词在句中充当成分，有时可以省略；同位语从句主要由that引导，在句中一般不做成分；句子也可以由when, where, how, why, w hether, w hat等词引导，充当成分(1) The news he told me is true.(2) The news that he has just died is true.(3) The problem that w e are fac ing now is how we can collect so much money. 定语(4) The problem how we c an c ollect so much money is diffic ult to solve.3、同位语从句和先行词一般可以用be动词发展成一个完整的句子，而定语从句不可以发展成一个完整的句子，(1) The idea that w e could ask the teac her for advice is wonderful. 同位语(2) The idea was that we could ask the teacher for advic e.(3) The fac t that the moon moves around the earth is known to all.(4) The fac t is that the earth moves around the earth.［定语从句］介词+关系词1）介词后面的关系副词不能省略。