Have to do - Responsibilities

Use 'have to' in the past, present and future to express responsibility or necessity. NOTE: 'have to' is conjugated as a regular verb and therefore requires an auxiliary verb in the question form or negative.


  • I have to arrive at work at 9 sharp. My boss is very strict.
  • We have to give him our answer today or lose out on the contract.
  • You have to pass your exams or the university will not accept you.
  • I have to send a report to Head Office every week.

Must do - Obligations

Use 'must' to express something that you or a person feels is necessary. This form is used only in the present and future.


  • I must go to bed earlier.
  • They must do something about it.
  • You must come and see us some time.
  • I must say, I don't think you were very nice to him.

Don't have to do - Not Required

The negative form of 'have to' expresses the idea that something is not required. It is however, possible if so desired.


  • I don't have to listen to this. I'm leaving.
  • You don't have to come if you don't want to.

Mustn't do - Prohibition

The negative form of 'must' expresses the idea that something is prohibited - this form is very different in meaning than the negative of 'have to'!


  • I mustn't eat chocolate. It's bad for me.
  • You mustn't phone me at work. We aren't allowed personal calls.
  • They mustn't see us talking or they'll suspect something.


Structure of Have to 


Structure of Must 



thanks it was very helpful for me..

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