一日一词【8】have to

have to

must表示“必须”。但是，人们更常用“have to”。它们之间究竟有何区别？

You must study hard. / You have to study hard.
上两句并无不同，但请看正面两句：

I don’t like this car. We must buy a new one.

The car doesn’t work. We have to buy a new one.

不难看出，must带有讲话者的主观音意愿，have to则表示客观需要，“只好”这样办。

have to在口语中常用作藉口。例如，想婉拒他人的邀请，便可藉口说，“Thank you very much. But I have to stay at home and study for the examination.”

have to的过去式时常作为must的过去时形式。例如：

He had to get up early yesterday.
昨天他必须早起。

值得注意的是，have to的否定形式及疑问形式，都要用助动词do。例如：

Why did you have to wait for him?
你为何一定要等他？

We don’t have to ask for his opinion.
我们不一定征求他的意见。