Expressing obligation/absence of obligation
Expressing obligation, absence of obligation and prohibition
Using the modals: must/ have to for obligation, must not for prohibition and don't have to for absence of obligation (possibility of choice).
To be a good pupil, you have to / you must do many things
and at the same time avoid others. (must not)
Also, there are things you are not obliged to do (don't have to).
Have to / Must | Must not | Don't have to |
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Must/ have to + verb (base form) : express obligation (necessity)
Must = have to
“Must”: is imposed by the speaker on himself. (inside motivation)
”Have to”: is imposed by someone/something else on the speaker.(outside obligation)
I must help poor people.
I have to eat healthy food. (the doctor says it’s necessary).
Prohibition/negative obligation (it’s necessary to not do something)
Must not = mustn’t = prohibition
You must not smoke here = don’t smoke here, it's forbidden!
do not (don’t) have to = absence of obligation/It’s not necessary to do it / you have the choice to decide
Don’t have to + verb (base form)
I can hear you! You don’t have to shout! = It’s not necessary to shout because I can hear you.
Look at the 2 examples:
- You don’t have to apologize. It’s not your fault = you are not obliged to do it / it’s not necessary to do it.
- You don't have to sleep at 8 p.m. You are not obliged, you can sleep at 10 p.m if you want.