「Must」 和 「have to」 都可以用來表示 「必須做……」 。然而，它們的否定形式 「mustn’t」 和 「don’t have to」 可能會讓人感到困惑。它們之中，哪個是 「絕對不能做」？哪個是 「可做可不做」？「一分鐘英語」 為你快速講解它們的區別。
Hi guys! This is Kee from BBC Learning English. Today, I’m going to tell you the differences between ‘mustn’t‘ and ‘don’t have to‘.
Now, ‘must’ and ‘have to’ are similar in meaning. They are both used to describe obligations. However, their negative forms are completely different in meaning.
We still use ‘mustn’t‘ to talk about obligations. For example: In the house, I mustn’t wear shoes. You know, to keep the house clean.
But ‘don’t have to‘ does not describe obligations, so the choice is yours! For example, if your teacher said: you don’t have to do your homework, well… then the choice is yours. You can say: Alright, I won’t!
Mustn’t and don’t have to
1. Modal verbs
Must, mustn’t, have to and don’t have to are modal verbs. This means they are always followed by a bare infintive verb. Unlike most modal verbs, have to and don’t have to change verb form when the subject pronoun changes. For example, becoming has to and doesn’t have to or had to and didn’t have to.
「Must、mustn’t、have to」 和 「don’t have to」 都是情態動詞，後接動詞原形。與多數情態動詞不同，「have to」 和 「don’t have to」 的動詞形態會隨著句中主格代名詞的變化而相應地變成 「has to、doesn’t have to、had to」 或 「didn’t have to」。
- I must go.
- We mustn’t go.
- You have to go.
- He doesn’t have to go.
2. Must and have to
Both must and have to refer to obligation. They explain what needs to be done.
「Must」 和 「have to」 兩者都可以表 「義務」，說明必須要做的事情。
- You must stop smoking. It will kill you.
- You have to go to school. It’s the law.
Mustn’t also refers to obligation, but in this case, it tells us what cannot be done.
「Mustn’t」 也可以用來表 「義務」，但用它來說明一件不能做的事情。
- You mustn’t talk to your mother like that.
- He mustn’t leave the house until I come home.
- We mustn’t eat any more chocolate.
4. Don’t have to
Don’t have to explains to us that there is no obligation to do something. As a result, we have free choice! You can choose to do this thing or not.
「Don’t have to」 用來說明不一定非要做某事。所以最終做與不做，可自行選擇。
- You don’t have to go to school if you are sick.
- She doesn’t have to come to the party, if she doesn’t want to.
- I don’t have to know all the moves to win the game!