定语从句是中学阶段的语法重点，也是历年高考的热点。 I.主语和谓语一致 1、关系代词在定语从句中 The boy who is standing at the door is my son. 2、在one of the +复数名词+定语从句”结构中，复数名词是先行词，关系代词在定语从句中作主语，其谓语动词用复数形式。例如： This is one of the best books that have ever been written on the subject. 3、在“the only one of the +复数名词+定语从句”结构中，one 是先行词，关系代词在定语从句中作主语，其谓语动词用单数。例如： This is the only one of the best books that has ever been written on the subject. II.关系代词的省略 在限制性定语从句中，关系代词在定语从句中作主语时不能省略；作宾语时在口语中可以省略。在非限制性定语从句中，关系代词不能省略。例如： A plane is a machine that can fly. The finger (that )I put into my mouth was not the one (that)I had dipped into the cup. Abraham Lincoln, who led the United States through these years, was shot on April 14,1865. His mother, whom he loved dearly, died in 1818. III. 正确使用that 和which 1、that 指物，有时也可以指人,which 指物，不能指人。Which 可以引导非限制性定语从句，也可以放在介词后面，that 则不能。 例如： Who is the man that is reading the newspaper?(正) Who is the man which is reading the newspaper?（误） The room in which she lives is a large one.（正） The room in that she lives is a large one.（误） 2、先行词前面有形容词最高级，序数词next, last, very, any, little, no 等修饰时，用that 不用which引导定语从句。例如： This is the best film that I have seen.（正） This is the best film which I have seen.（误） 3、先行词是all, much, little, none等时，用that而不用which引导定语从句。例如： That’s all that I want to say.（正） That’s all which want to say.（误） 4、先行词是不定代词something, anything, anything, everything时，一般用that而不用which引导定语从句。例如： Is there anything that you want in this shop?（正） Is there anything which you want in this shop?（误） 注：当something表示具体的事物，重要的东西，重要的人物等确定意义时，它是名词，关系代词用that 或which均可。例如： There was the mysterious something which/that they had worked so hard to find: radium. 5、先行词是人和物时，要用that 而不用which/who引导定语从句。例如： He talked about some writers and books that were unknown to us all. （正） He talked about some writers and books which/who were unknown to us all.（误） 6、先行词本身是that 时，一般用which引导定语从句。例如： The predicate is that which is said of the subject. 7、在who开头的疑问句中，若还要用关系代词引导定语从句时，用that引导定语从句。例如： Who is the girl that is singing in the hall? 8、当关系词后面有插入语时用which引导定语从句。例如： Here is the English grammar book which, as I have told you, will help to improve your English. IV.定语从句要用关系词引导。 例如： I have three friends, none of whom can speak French.（正） I have three friends, none of them can speak French.（误） 注：若把逗号“，”改为分号“；”误句也就变为正确的句子了。 V.先行词受such, the same 修饰时，通常用as 引导定语从句。 例如： This is not such a book as I want. This is the same book as I want. 试比较：the same…as 与the same …that This is the same knife as I lost.这把刀跟我丢的是一模一样的。（两把刀） This is the same knife that I lost.这把刀就是我丢的。（一把刀） VI. as和which指整个主句的内容，引导非限制性定语从句的区别。 as和which指整个主句的内容，引导非限制性定语从句有时可以通用。as引导的定语从句可以位于句首、句中或句末；which 引导的定于从句一般只位于句末。as引导的定语从句常与know, see, report, say, expect, announce等动词连用；which引导的这类定语从句时常作实意动词的主语，当它引导的从句与主句之间含有并列关系或结果关系时，一般用which。例如： As we all know ,China is a country with a long history. China is a country with a long history, as is known to us all. Tom did not pass the exam, which made his mother very angry
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