that的八种用法：1.that作指示代词；2.that作指示形容词；3.that作关系代词引导定语从句；4.that作连词等。
1.that作指示代词
That is my book.那是我的书。
2.that作指示形容词
We haven't found any solution to deal with that problem yet.我们仍未找到解决问题的办法。
3.that作关系代词引导定语从句
This is the sort of thing that Jeremy loves.这是杰里米喜欢的东西。
4.that作连词
that可以作连词引导各种名词性从句，包括宾语从句、主语从句、同位语从句和表语从句。
1)that作连词引导宾语从句
They have recommended that the site be closed and repaired. 他们建议将该处关闭并进行维修。
2)that作连词引导主语从句
That you will win the medal seems unlikely. 你想获得奖牌看起来是不可能的。
3)that作连词引导同位语从句
The idea that modern art can only be seen in museums is mistaken. 现代艺术只能在博物馆才能见到的想法是错误的。
4)that作连词引导表语从句
One problem is that I don't look any different from other people. 有一个问题是我看起来和其它人没有任何不同。
that还可以作连词引导结果状语从句，阅读时需要留意这个用法。
What was the matter with the fellow that he looked so happy? 那人怎么回事，看起来这样高兴?
5.that作副词
that和this都可以作副词，用于修饰形容词或修饰另一个副词，表示“这么，那么，如此，这般”的意思，如:
It's about that long. 它大约有那么长。
1)由that引导的状语从句。
What have I done that you should treat me like this? 我究竟干了什么，你竟这样对待我？
2)结果状语从句中的that 有时还可以省列。
He is such a marvelous joker you can't help laughing. 他的笑话讲得那么出色，你会禁不住哈哈大笑。
从结构的角度讲，区分that是引导状语从句还是引导定语从句可以根椐从句的成分是否完整来判断。定语从句通常是不完整的，即从句所修饰的先行词会在从句中充当某成分。如：It is a story that people believe. 这是一个人们都相信的故事。(这里story作believe的宾语。)
