must 和 have to
- must 侧重于个人意志和主观上的必要。have to 侧重于客观上的必要，可用于现在时、过去时和将来时。例如：
I know I must study hard. 我知道我必须努力学习。
My brother was very ill, so I had to call the doctor in the mid-night.
I haven’t got any money with me, so I’ll have to borrow some from my friend.
He said they must work hard.他说他们必须努力工作。
- have to可以用于多种时态；而must只用于一般现在或将来。例如：
The composition is due to hand in this morning, so I had to finish it last night.