butandthan引导定语从句.docVIP

浅谈but和than引导的定语从句在初级英语阶段，学生知道引导定语从句的关系代词有who (whom, whose),that和which等。到了中高级阶段，这些显然是不够的。还应了解but和than也可以用作关系代词的情况，以拓宽知识面，提高语言识别和理解能力。 1.but在英语句子中可用作关系代词，引导定语从句。但应特别注意but虽然形式上是肯定的，意义上却是否定的。这正是but和其它关系代词(who, that , which等)不同之处。例如： (1)There is no rule in English but has exceptions.英语中没有无例外的规则。 (2)There is no old habit but may be cured by a strong will-power.通过强大的意志力没有改不了的旧习惯。 (3)With the introduction of the electronic computer, there is no complicated problem but can be solved in a few hours.由于引进了电子计算机，没有在几小时内解决不了的复杂问题。 (4)There is no human being but errs.没有不犯错误的人。 如果将以上例句(1)、(2)和(3)中的关系代词but改成that，或者将例句(4)中的关系代词but改成that或who,那么定语从句必须改成否定从句才能与原句意义相一致。例如： (5)There is no rule in English that has no exceptions/ that has not any exceptions. (6)There is no old habit that may not be cured by a strong will-power. (7)With the introduction of the electronic computer, there is no complicated problem that cannot be solved in a few hours. (8)There is no human being that(who)makes no mistakes/that(who)does not makes any mistakes. 【注意】如果(5)、(6)、(7)、(8)中没有明确的否定词no或not any等，其意义则完全相反。 2.than也可以用作关系代词，引导定语从句，但要注意主句中必须有比较级字样和than前后呼应。例如： (9)He smoked more (fewer) cigarettes than (he bought.) were normally available.他吸的香烟比他买的（弄到的）要多（少）。这里than在语法功能上相当于that/which的功能，但是这里不能改成后者，因为主句中有比较级more。 请再看下列的例句： (10)We often advise him not to drink more wine than is good for his health. 我们经常劝他为了身体健康不要喝过量的酒。 (11)He often sat in a small bar drinking considerably more wine than was good for his health.他经常坐在小酒馆里，喝过量的酒。这不利于他的身体健康。 (12)To understand the situation completely requires more thought than has been given thus far.要彻底理解这种局势需要作比迄今为止更多的思考。 如果我们仔细观察一下，就会发现，例句(9)中的名词cigarettes用的是复数形式，所以从句就用了复数形式的动词were,而在例句(10)、(11)和(12)中由于所用从句中便分