Lack of Obligation and Prohibition

1Công thức

2Giải thích

Don't have to/don't need to/needn't nghĩa là 'không cần', còn mustn't nghĩa là 'cấm'. Needn't have + V3 nghĩa là đã làm nhưng thực ra không cần thiết; didn't need to/didn't have to không cho biết hành động có xảy ra hay không.

Don't have to, don't need to and needn't mean that something is not necessary, whereas mustn't means that it is forbidden. In the past, needn't have + past participle means the action happened but was unnecessary, while didn't have/need to does not say whether it happened.

3Khi nào dùng

• Saying something is not necessary
• Prohibiting an action
• Unnecessary past actions

4Quy tắc cần nhớ

• You mustn't ... = Don't do it; you don't have to ... = it's optional
• Needn't have + past participle always refers to something that was done
• Didn't need to/didn't have to can refer to something that was or wasn't done

5Ví dụ

• You mustn't touch the exhibits in the museum.

• You don't have to pay now; you can pay on arrival.

• I needn't have brought an umbrella, because it stayed dry.

6Lỗi thường gặp

• You mustn't bring a pen. We provide them. (you don't have to bring)
• We needn't to hurry. (needn't hurry / don't need to hurry)

7Dễ nhầm với

Modals of Obligation and Necessity