新概念二 L17 ：must 与have to的辨析

must 是情态动词

表示：1. “必须”，用于一般疑问句时，否定回答用needn't或not have to;否定式是mustn't “禁止；绝对不能”。 例句：We must be careful when crossing the street.

Must I hand in my homework today? Yes, you must. No, you needn't/don't have to

It's no parking area. You mustn't park your car here. Or you will receive a ticket.

2. “一定是”，表示猜测，只用于陈述句的肯定句。否定句中表示“不可能是”，用can't。

例句：He must belong to the soccer club.

It must be Tony's bag. There is his name on it.

The man at the school gate can't be our headmaster. He is having a meeting in his office.

have to do sth. 也是一种特殊的情态动词。

表示“不得不；必须”。往往表示客观上的原因。有各种时态。

例句：We couldn't afford to take a taxi. So we had to walk home.

Now it's nearly 8 o'clock. You have to hurry up. Or you will miss the train.

The weather forecast says it will be rainy tomorrow. The children will have to stay indoors.