Unit 7.1

Must vs Have to


Both must and have to belong to the group of auxiliary modal verbs that have no meaning on their own but they modify the main verb, change its meaning and give more details about the action.

Must and have to are used to express certainty, necessity or strong obligation which comes from internal or external factors.


Must and to have to have different positions in the sentence.

{see Must: Modals of Obligation and Have to: Modals of Obligation, A2 level }


  • I must stop eating sweets (I want to do it).
  • I have to stop eating sweets (my doctor ordered me to stop).
  • You mustn’t read this book (you are not allowed).
  • You don’t have to read this book (you have a choice to read it or not).
  • Must you wear the same suit every day (is it necessary for you)?
  • Do you have to wear a suit at work (is it obligatory at your workplace)?


We use must for strong obligations and necessities that come from us, for example from our personal opinion.

We use have to for strong obligations and necessities that come from our social context, for example regulations and orders that come from someone else.


Must and have to are two modal verbs which are used to express strong obligation or the need to do something:

  • Must expresses strong obligation which comes from inside. Mustn’t usually expresses prohibition;
  • Have to is generally used to show that there is an obligation imposed by external factors. Don’t have to usually expresses that it is not necessary to do something.

For example:
— “I must start a diet, I do not like my appearance.” = The subject chooses to start a diet because of personal reasons.
— “I have to start a diet, the competition is soon.” = The subject is obliged to start a diet because of external reasons.

NOTE: The form of must is always the same, whereas have to changes to has to in the third person singular.

Let’s revise this content within the {Form} section. Take a look at the {Example} section that shows its use within a context.