1.定语从句：修饰一个名词或代词的从句称为定语从句,一般紧跟在它所修饰的先行词后面.2.关系词：引导定语从句的关联词称为关系词,关系词有关系代词和关系副词.关系代词有that,which,who,whom,whose,as等；关系副词有where,when,why等.关系词常有3个作用：1,引导定语从句.2,代替先行词.3,在定语从句中担当一个成分.,名词,代词,数词,分词,副词,不定式以及介词短语来担任,也可以由一个句子来担任． 定语从句是由关系代词或关系副词引导的从句,其作用是作定语修饰主句的某个名词性成分,相当于形容词,所以又称为形容词性从句． I.限制性定语从句的特殊用法 II.非限制性定语从句 III.同位语从句 IV.同位语从句和定语从句的区别 I.限制性定语从句的特殊用法 1.way + 定语从句 way 后面跟定语从句有三种形式.(1) way + in which + 定语从句 例如：She was pleased with the way in which he had accepted her criticism.(2) way + that +定语从句 例如：They didn’t do it in the way that we do now.(3) way + 定语从句 例如：He didn’t speak the way I do.2.as 引导的定语从句 (1) 在由 as 引导的定语从句中所修饰的词（先行词）前面常有 such 或 the same.例如：Such people as you describe are rare nowadays.I have the same trouble as you (have).(2) As 在定语从句中可以作主语、宾语或表语.例如：Let’s discuss only such questions as concern everyone of us.（作主语） I never heard such stories as he tells.（作宾语） I’ve never seen such a clever man as he is.（作表语） (3) As 有时引导非限制性定语从句,可在定语从句中作主语、宾语、表语,修饰主句,常解释为正如、如同.例如：As is known to all,the earth moves round the sun.（作主语） As was expected,he performed the task with success.（作主语） As he predicted,the wind changed.（作宾语） The meeting is very important,as indeed it is.（作表语） II.非限制性定语从句 1.非限制性定语从句由 who,whom,which 引导（不可用 that）,还可以由 whose,when,where 等词引导.非限制性定语从句要用逗号隔开,非限制性定语从句可以删去,整个句子的意思还是完整的,而限制性定语从句如果被删去,句子的意思不完整.例如：Mr Brown,who is our English teacher,lives near our school.Yesterday I met my son’s school master,whom you saw at my home last year.He has finished the difficult exercise,which is easy for you.The factory is headed by a 35-year-old man,whose wife is from America.They will fly to Qingdao,where they plan to stay for two weeks.In these days,when I was a child,the city had no industry to speak of.注意：非限制性定语从句中的关系词是不可省略的.2.非限制性定语从句有时并非修饰名词或代词,它可以修饰整个句子.例如：They have invited me to visit their country,which is very kind of them.3.in front of,at the back of,in the middle of 等短语在定语从句中的用法.如果关系代词是作这类介词短语的宾语时,介词短语必须提前.例如：Yesterday afternoon we arrived at his log cabin,in front of which stood a tall tree.4.注意此类句子表达方式.There are forty students in their class,thirty of whom are League members.也可以改成 There are forty students in their class,of whom thirty are League members.III.同位语从句 同位语从句常跟在 idea,fact,doubt,thought,belief,news,hope 等词后面,由连接代词 that（不可用 which）和连接副词 when,where,whether 等引导.例如：I had no idea that you were here.The fact that he is unfit for his job is quite clear.Then arose the question where we were to get the machine needed.All the time she was in bitter doubt whether she was right.IV.同位语从句和定语从句的区别 同位语从句用于名词后面,对该名词的内容作进一步说明,连接词在从句中不作成份.定语从句用于修饰名词或代词,引导定语从句的关系代词或关系副词往往在定语从句中作一个成份.例如：Have you heard the news that Mr Smith will come to give a lecture on Irish Fairy Tales?这里that 引导的是同位语从句,不可以用 which 代替 that,连接代词在从句中不作成份.Have you told him the news that I told you last week?这里that 引导的是定语从句,可以用 which 代替 that,它在定语从句中作宾语