Learn the differences between these Modal Verbs: Must vs. Have to, and Mustn’t vs. Don’t/Doesn’t Have to…
Must vs. Have to
– Express personal obligation
– Express what the speaker thinks is necessary
– Express subjective obligation
You must work hard.
All passengers must wear seat belts.
– Express impersonal obligation
– The subject is obliged or forced to act by a separate, external power (for example, the Law or school rules)
– Express objective obligation
I have to leave early today.
You will have to pay for the excess.
Mustn’t vs. Don’t/ Doesn’t Have to
Mustn’t/ Must not
It is prohibited; it is not allowed. It is important that you do NOT do something. The prohibition can be subjective (the speaker’s opinion) or objective.
Children mustn’t talk to strangers.
Cars mustn’t park in front of the entrance.
Don’t/ Doesn’t Have to
There is no obligation; you are not required to do something, especially if you don’t want to.
You don’t have to make excuses for her.
You don’t have to whisper, no one can hear us.