定语从句的引导词什么时候可以省略？

关系代词指代先行词在定语从句中作表语时只用that,但时常省略。

1、在从句中充当宾语The people(who,whom,that)I saw yesterday were from Japan.

2、在从句中作介词宾语，且介词在句尾Here is the man (that,who,whom)looking for.

3、在从句中作表语Shanghai is no longer the city(that,which)it used to be.

4、在There be句型中，作主语的关系代词There's somebody(who)wants to see you.

5、先行词是表示方式，原因，时间（像way,reason,day),in which,for which,when,that等可省I don't like the way (that)you talk to me.I like the place for the reason(that,for which)you dislike it.

除了关系副词（where/why/when)，关系代词(which/who/whose/that/whom)在先行词作定语从句中作宾语的时候可省略．
如：
This
book
(that/which)i
bought
have
been
lent
to
my
classmate.这里”书”作宾语，所以关系代词可省略．
但若前面有介词，则不可省略，如：
The
girl
with
whom
i
went
shopping
is
my
sister.(也可说:The
girl
who
i
went
shopping
with
is
my
sister.)

主要是定语从句：先行词在从句中当宾语时，关系代词（引导词）可以省略。