定语从句既是NMET命题的热点，又是中学英语教学中的重点和难点。其中有些句子是有关定语从句的，但也有些句子貌似定语从句而实际上是其它句型、句式，有的即使是定语从句却也截然不同。现将这些句子集中在一起进行对比并作简析，以供参考。

　　1.(1)There are two boys in Peter's，

　　both of whom are white.

　　(2)There are two boys in Peter's,and both of them are white.

　　析：句(1)是含有定语从句的复合句。句(2)因为有并列连词and所以是并列句。

　　2.(1)This kind of plant grows best at the places where it is warm and wet.

　　(2)This kind of plant grows best

　　where it is warm and wet.

　　析：句(1)是由关系副词where引导的定语从句，修饰先行词places,这时的where也可以由at which代替。句(2)是由连接副词where引导的地点状语从句，这时的where不可以由介词＋which代替。

　　3.(1)John is one of the students who know English.

　　(2)John is the only one ofthe students who knows English.

　　(3)One of the students knows Eng- lish.

　　析：句(1)、(2)都是定语从句，在"the(only)one of＋复数名词＋定语从句"结构中，先行词是one，而不是复数名词，故定语从句谓语动词用单数，但有"oneof＋复数名词＋定语从句"句型中，先行词是复数名词，故定语从句谓语动词用复数。句(3)不属于定语从句的范畴，只是一个简单的主谓一致关系。句中的主语是one，故谓语动词用单数。

　　4.(1)Here is such a heavy stone as I can't move.

　　(2)Here is such a heavy stone that I can't move it.

　　析：句(1)是定语从句，先行词前有such修饰时用as引导，as在定语从句中作move的宾语。句(2)是such...that引导的结果状语从句。

　　5.(1)As is known to us all,the light on the earth is given by the sun.

　　(2)It is known to us all that the light on the earth is given by the sun.

　　析：句(1)是由as引导的非限制性定语从句，这时的定语从句的位置很灵活，可以位于句首，句末或插在句中。as代替整个主句，在定语从句中充当主语。句(2)是含有主语从句的复合句，it作形式主语，真正的主语是that引导的从句。

　　6.(1)The sun is bigger than the moon, as we all know.

　　(2)The sun is bigger than the moon,and we all know it.

　　析：句(1)是由as引导的非限制性定语从句，as代替整个主句，在定语从句中作know的宾语。句(2)是由and连接的并列句。

　　7.(1)Was it October 1,1949when the People's Republic of China was founded?

　　(2)Was it on October 1,1949that the People's Republic of China was founded?

　　析：句(1)是由关系副词when引导的定语从句，从句的when也可以由on which代替。句(2)是强调句型，强调句中时间状语on October 1,1949特别要注意句(2)中October之前的on。

　　8.(1)I'll never forget the days that/ which I spent with him.

　　(2)I'll never forget the day when I was born.

　　析：句(1)、(2)都是定语从句，但句(1)中先行词days在定语从句中作spent的宾语，故定语从句由关系代词that／which引导，也可省略。句(2)中先行词day在定语从句中作时间状语，故定语从句可由关系副词when或on which引导。

　　9.(1)He failed in the exam again,as was expected.

　　(2)He failed in the exam again,which was not what he had expected.

　　(3)He failed in the exam again,which made his parents angry.

　　析：这三个句子都是非限定性定语从句，只是引导词不一样，而且as,which决不能互换。句中的as和which都是用来代替主句，而不是某个先行词。as可以放在句首，有"正如"之意，which不能放在句首，无"正如"之意。且定语从句是否定句时，用which而不用as。

　　10.(1)I believed the man who I thought was honest.

　　(2)I believed the man whom I thought to be honest.

　　析：句(1)who作定语从句的主语，故用主格，句(2)whom作thought的宾语，故用宾格。

　　11.(1)On may 5we reached Beijing, where we stayed for a week.

　　(2)On may 5we reached Beijing, and there we stayed for a week.

　　析：句(1)属于由where引导的非限制性定语从句，先行词Beijing在定语从句中作地点状语。句(2)则是由and连接的并列句，there在句中作状语。

　　12.(1)Give me the reason why you are late.

　　(2)The reason that he gave us was unacceptable.

　　析：句(1)是why引导的定语从句，相当于for which。句(2)是that引导的定语从句，that在定语从句中作gave的宾语。

　　13.(1)The news that he told me is true.

　　(2)The news that he will come back from the U.S.is true.

　　析：句(1)是that引导的定语从句，that在定语从句中作told的直接宾语。也可以由which代替。句(2)是that引导的同位语从句，that在同位语从句中不作任何成分，只起连结作用，但一般不能省略，也不能用which代替。

　　14.(1)The house whose roof was damaged has now been repaired.

　　(2)The house the roof of which was damaged has now been repaired.

　　析：句(1)，(2)都是定语从句，whose＝of which,但whose必须在无定冠词the的名词前，而of which常放在有定冠词the的名词后。

　　15.(1)This is the same key as I lost yesterday.

　　(2)This is the same key that I lost yesterday.

　　析：句(1)和句(2)都是定语从句，但含义不同，句(1)是由as引导的，一般用在the same...as结构中，表达的意思是"像……一样"；故句(1)的意思是"这把钥匙和我昨天丢的那把很像。"而句(2)是由that引导的定语从句，句(2)的含义是"这就是我昨天丢的那把钥匙。"

　　(文/山西省实验中学王少勋；英语辅导报高中教师版03-04学年第19期；版权归英语辅导报社所有，独家网络合作伙伴新浪教育，未经许可，不得以任何形式进行转载。)