一、用作主语

The second is yours. 第二个是你的。

It’s said that 13 is an unlucky number. 据说13是一个不吉利的数字。

二、用作表语

Her father is sixty-five. 她父亲65岁。

Two thirds of the apples were bad. 三分之二的苹果是坏的。

三、用作宾语

I know three of them. 他们当中有三个有我认识。

Please give me the third. 请给我第三个。

四、用作定语

He has three English dictionaries. 他有三本英语词典。

The second one is more expensive. 第二个更贵。

The rope is only 2.15 meters long. 这根绳子只有2.15米长。

五、用作同位语

Are you two reading? 你们两人都在看书吗？

Let us four finish the work. 让我们四个人完成这工作吧。

Who is that man, the first in the front row? 前排第一个是准？

六、用作状语

I hate riding two on a bike. 我不喜欢骑自行带人。

Think first, then act. 先想清楚再行动。

We agree with you a hundred percent. 我们百分之百同意你。