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 havent 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。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。