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Must/mustn’t
Use must + infinitive without to
Must is a modal verb, and modal verbs are followed by an infinitive without to.
No -s
Modal verbs don’t add -s after he/she/it.
Use must/mustn’t in negatives and questions
Must is an auxiliary verb. This means that it has a negative and an interrogative size. Do not use do/did in negatives and questions.
Have to/don’t have to
Use do and did in negatives and questions
The verb have in have to is not an auxiliary verb. Use do/don’t, does/doesn’t, did/didn’t in questions and negative sentences in present and past.
No contraction
The verb have in have to cannot be contracted đồ sộ ‘ve.
Past and future forms
Only have to has a past and a future size. Must does not have a past or a future size.
Must vs have to / mustn’t vs don’t have to – Use
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Have to
Rules and obligations
We use have to đồ sộ talk about rules and obligations, something that is necessary.
- I have đồ sộ get đồ sộ work before 7 tomorrow.
- The siêu xe broke down and we had đồ sộ call a xe taxi.
Must
Rules and obligations
Must is very similar đồ sộ have to. We use must + infinitive (without to) đồ sộ talk about rules and obligations.
- I must go đồ sộ the doctor.
- I must get up early tomorrow.
Don’t have to
Don’t need đồ sộ – not necessary
If you don’t have to tự something, it means that you ‘don’t need to’ tự something (there is no obligation). You can tự it but you don’t need đồ sộ tự it if you don’t want đồ sộ tự it.
- You don’t have đồ sộ pick mạ up at the station. I can take a xe taxi. (=You can pick mạ up, but you don’t need đồ sộ tự it).
Mustn’t
Prohibition
Use mustn’t đồ sộ talk about something that you can’t tự. It’s necessary that you don’t tự it.
- You mustn’t call mạ before 8. (=You can’t Gọi mạ before 8.)
- I mustn’t lose my concentration now.
Must vs have to
Must
Obligation from the speaker
We normally use must đồ sộ talk about obligations that come from the opinion of the speaker. The speaker thinks it’s necessary or important đồ sộ tự something.
- MANAGER: You must get up early tomorrow. The meeting is at nine. (=The obligation comes from the manager. The manager thinks it’s necessary.)
- DOCTOR: You must stop smoking. (=It’s the doctor’s opinion. The doctor thinks it’s necessary.)
- SMOKER: I must stop smoking. (=It’s the smoker’s opinion. The smoker thinks it’s necessary đồ sộ stop smoking.)
Have to
External obligation
We normally use have to when there’s an external obligation. The obligation doesn’t come from the speaker’s opinion; another person thinks it’s necessary.
- WORKER: We have đồ sộ get up early tomorrow. The meeting is at nine. (=The obligation comes from the manager, not from the worker.)
- SMOKER: I have đồ sộ stop smoking. (=It’s the doctor’s opinion, not the smoker’s opinion. The doctor thinks it’s necessary.)
Mustn’t vs don’t have to
Don’t have to
You don’t need đồ sộ tự it; not necessary; no obligation
Don’t have to and mustn’t have opposite meanings. We say that we don’t have to tự something when we don’t need to tự something; we can tự it, but it’s not necessary.
- You don’t have đồ sộ wait here. (=You can tự it, but it’s not necessary)
Mustn’t
Prohibition; it’s necessary that you don’t tự it
We say that we mustn’t tự something when we cannot tự something; it is necessary that we don’t tự something.
- You mustn’t wait here. (=You cannot tự it; it’s against the rules)