1. 特指某些人或某些事物, 例如：
The book on thedesk is mine．
Beijing is thecapital of China.
2.指谈话双方都知道的人或事物.例如：
Open the window, please.
Let' s meet on the road outside the school gate．
What do you think of the film?
3.指上文提到的人或事物。例如：
I saw a boy. The boy was crying.
I have a bird. The bird is white.
I bought a coat.This is the coat.
4.用于世界上独一无二的事物前面。例如：
We have friends all over the world.
Which is the biggest, the sun，the moon or the earth?
the sky， the world
The moon goes around the earth.
5. 用于单数名词前表示一类人或事物
The horse is a useful animal.
The apple is a kind of fruit.
这种情况还有另外两种表达
An apple is a kind of fruit.
Apples are a kind of fruit.
请注意，不是说没有the+复数名词的情况，是说在泛指的情况下没有，特指是可以的。
6. 用于含有普通名词的专有名称前
the United States of America
the People’s Republic of China
the United Nations
组合专有名词 the USA; the UK
