must/have to

must 着重表示说话人主观上的看法,有很强的个人色彩。例如,Doctor: You must give up smoking.

1. You must see the doctor. 你必须去看病。

2. I must be off. 我必须离开了。

3. The dog must die. 那条狗必须死。

have to 则着重表示客观上的“必须”，如其他人、法律、自然规律、政府要求的事：

1. Mrs. Cherrell and I have to go to a meeting now. (Galsworthy) 柴瑞尔夫人和我现在必须去参加一个会议。

2. We have to pay our taxes to the government. 我们必须向政府交税。

3. I had to leave early because I wasn't feeling well. 因为我感觉不舒服,我必须提前离开。

但这种区分不是绝对的。许多人甚至不承认有这种区别。