英语中使用that
1.先行词如果有all, every, only, very, any (任何的)，one of few,any,little, no等词修饰时，
2.先行词是不定代词，some（something，somebody，someone），any（anything，anybody，anyone），no（nothing，nobody，no one），every（everything，everybody，everyone
3.先行词有最高级修饰
4.先行词有序数词修饰，
5.先行词如果既有人又有事物
6. 主句以There be…开头,先行词为物时用that,先行词为人的句子中,常用who引导定语从句.
. There is a room in the building that is still free.
There is a pretty girl who wants to see you.
7. 句子中如果已经有了who，引导词代替人，为了避免重复，要使用that；或者句子中如果已经有了which，引导词代替事物，为了避免重复，要使用that；
8. 先行词如果在主句中做表语，或引导词在从句中做表语，代替事物，多使用that；eg. 这是我昨天买的书。

This is the book that I bought yesterday.
as作为定语从句引导词的三点用法
（1）代替主句整句话内容；
（2）先行词有such修饰，要使用as；
eg. He is such a good teacher __as__ we all like.
He is such a good teacher __that___ we all like him.
(such…that 如此…以至于…,引导结果状语从句)；
（3）先行词有the same修饰，
the same……as表示同类不同一个：I want to buy the same bicycle as my friend did.
the same……that表示同类同一个：The police has found the same bicycle that Jack lost.
引导词代替主句整句话内容，在从句中做主语或宾语，要使用as或which来引导
❀as和which的区别：
1.结构上as的从句既可以放于主句前，也可以放于主句后；which的从句只能放于
主句后；
2.as如果在从句中做主语，谓语动词只能是be动词结构；
eg. 她数学考试不及格，这让她的爸爸很生气。

She failed her math test，__A__ made her father angry.
A. which;
B. that;
C. as;
D. it;
E. this;
只用which而不用that引导定语从句
1．在非限制性定语从句中
2．当先行词本身是that或是those且指物时.
Eg. Paul has found that which he lost yesterday
3．当关系代词前面有介词时,常用which引导定语从句.
Eg. I like to live in the house, in front of which there is a tall pine tree
另外：there be 结构中若是否定结构,后常用but,这时相当于who/that…not. Eg. In China, there is no one but knows Beijing.。