在英语中that和which可以省略的从句是定语从句，省略的条件是现行词在从句中作宾语才可以省略，其他情况则不可以省略。

相关介绍

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.

例如1：I can't find the book (which/that) I bought last month. 现行词the book在从句中作bought的宾语，可以省略。

例2：The book which / that was bought last month was lost yeaterday. 这题现行词the book在从句中作主语，此处不能省略。

还有一种that可以省略的的从句，就是宾语从句。

例如：Our teacher suggests (that) we should read English every day. 这里suggests后面的是宾语从句，that可以省略。

注意：如果一个动词后面接两个或者两个以上的宾语从句时，第一个从句的that可以省略，但从第二个从句开始that不能省略。

例如：The teacher said (that) we should read English every day and that there would be an English exam next week.这里said连接两个宾语从句，第一个从句的that可省可不省略，第二个不可以省略。