作者:杨秀祥
情态动词have to (口语中说成have got to) 表示客观需要做的事情,意为“必须;不得不”。它和其他情态动词相比较,有很多不同之处,现在就将其用法要点小结如下:
一、have to同情态动词must 的区别。have to 和must 都有“必须”的意思。但是 have to侧重于强调客观条件需要做的事情。而must 侧重于表示说话人的主观看法,认为有义务,有必要去做某事。例如:
1. I have to clean my room first.
2. You must be here before eight.
二、have to 有人称和数的变化,其他情态动词没有。例如:
1. Mr Green has to work on the farm all day.
2. I / He can swim in the river.
三、have to有多种时态的变化,而can, may等只有过去式等形式。例如:
1. We will have to ask Li Lei instead.
2. I thought I could smell something burning.
四、have to不能直接用来否定或提问,需要助动词do / did / does等帮助。而其他的情态动词一般都可以直接进行否定和提问。例如:
1. What does she have to do?
2. You don't have to help her with her homework.
3. May I come in?
五、have to可以被may 等情态动词修饰,其他动词之间不能互相修饰。例如:
I think you may have to finish the work today.