This book is about Chinese traditional medicine.这是一本关于中医的书。(作定语)
指示代词ins，these，that， those的其它用法
1)This (these)常用来指在时间或空间上较近的事物，that(those)则常用来指时间或空间上较远的事物。如：
This is a sickle and that is an axe.这是一把镰刀，那是一把斧子。
These days are cold.这些天很冷。
In those days the poor people had a hard time.在那些日子里，穷人生活很苦。
2)有时that和those指前面讲到过的事物，this和these则指下面将要讲到的事物。如：
I had a bad cold. That's why I didn't come.我伤风很厉害，所以我没有来。
Those two statements are not true.那两种说法是不真实的。
What I want to say is this：Pronunciation is very important in learning English.我所要说的是：语音在英语学习中非常重要。
chairman Mao honoured Lin Hulan with these words："A great life A glorious death"毛主席用下面的话表彰刘胡兰："生的伟大，死的光荣。"
3)有时为了避免重复提到过的名词，常可用that或those代替。如：
The climate of shenyang is just as good as that of Beijing. 沈阳的气候跟北京的一样好。(that代替climate)
The county's grain output of 1981 was double that of 1970.这个县1987年的粮食产量比1980年增加一倍。(that代替grain output)
Television sets made in Nanjing are just as good as those made in Shanghai.南京出产的电视机和上海的一样好。(those代替television sets)
4)This和that有时作状语用，表示"程度"，意谓"这么"和"那么"。如：