我們經常用must或者have to說明“必須要做......”,有時候這兩個詞並沒有多在區別,可以相互替換。
- It's late, I must go now. 或者 It's late, I have to go now.
表達上的區別
但是,在兩者這間其實有一個區別,而且有時候在表達上相當重要。
Must更多表達主觀意願上的“必須”,當我們在表達個人感受的時候,用must。
- I haven't phoned Kofi for ages. I must phone him today.
我已經好久沒給Kofi打電話了,我今天必須打給他。
- I haven't got much more time, I must hurry.
我已經沒有更多的時間了,我必須趕緊地。
Have to更多是非主觀意願上的“必須”,可能是因為一些規則,或者情況,導致你“必須”去做,所以更多說是“不得不”。
- You can't turn right here, you have to turn left.
你不能在這右轉,這兒必須左轉。(因為交通信號燈的規定)
- My eyesight isn't very good, I have to wear glasses when I read books.
我的視力不是很好,讀書的時候我必須帶眼鏡。(因為眼睛視力差的情況)
時態使用上的區別
must可用於現在時態和將來時態的表達,但是無法在過去時態中使用。
- I must go now. The train will leave in 10 minutes.
我必須走了,列車10分鐘之後就開。
- I must go back home tomorrow.
我明天必須回家。
但是,沒有I must go yesterday/ last night(X) 這種說法。
而have to,則可以應用於各種時態裡。
- Have you had to go to hospital?(現在完成時態)
- I had to go to hospital.(過去時態)
不過要注意,have to 在疑問句,否定句中,要和助動詞do/did/does搭配使用。
- Why did you have to go to hospital?
- What do I have to go to hospital?
- Kofi does have to work on Saturday.
否定形式上的區別
mustn't 是表明某件事你必須“不能”做。
- You musn't tell anybody about this, keep it as a secret.
你不可以告訴任何人這件事,把它當作秘密。
而don't have to 則是表明某件事你不需要一定要做,可做可不做。
- I don't need to work tomorrow, so I don't have to get up early.
我明天不用工作,所以我不需要早起。
在這個層面上,don' have to 和 don't need to 意思有點相近,都是“沒必要去做”。
- We've got plenty of time. We don't need to hurry.
我們有許多時間,不需要著急。
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