定语从句:指人时常用which 和 who 而 what 则常用于指物
名词性从句分为:主语从句,宾语从句,同位语从句和表语从句.
what可以引导名词性从句,在从句中可做主语、宾语、表语.
which是关系代词,引导定语从句,在从句中可充当主语、宾语、表语.引导定语从句的词分为关系代词(which,that,who,whom,whose,as)关系副词(when,where,why),注意:没有what.
如:
1.This is the book which I talked about yeasterday.
(which引导定语从句放在名词book后面起修饰作用,which在从句中充当talk about的宾语)
2.This book is what I talked about yesterday.(what引导名词性从句,放在is之后,what 在表语从句(名词性从句)充当talked about的宾语.)
that可以指人,也可以指物;which只能指物
2.当先行词是不定代词all,something,anything,everything,none,the one等时,只能用that
3.先行词前有形容词的最高修饰时,要用that
4.先行词前有序数词修饰时,要用that
5.先行词前有形容词only,very,few,little等修饰时,要用that
6.先行词既指人,又指物时,只能用that
7.在非限制性定语从句中,只能用which
8.在介词+关系代词引导的定语从句中,必须用which
9.当先行词本身是that的时候,要用which