must, have to, and other must uses
must and have to for obligation; must not for prohibition; must for logical deduction.
A — Sample sentences
Words like headache, cough, medicine, bandage, temperature, and feel sick.
1) must / have to — obligation
must = speaker's authority; have to = external rules. Past: had to.
- You must take this medicine three times a day.
- I have to see the doctor before I go back to work.
- She had to stay in bed when her temperature was high.
- We must not ignore a bad cough for too long.
2) don't have to — no obligation
It is not necessary (different from must not).
- You don't have to take a bandage if the cut is small.
- He doesn't have to see a specialist — his headache is better.
- They didn't have to go to hospital — the injury was minor.
- You don't have to finish all the medicine if you feel well.
3) must — logical deduction (present)
We are almost sure something is true.
- She has a sore throat and a cough — she must have a cold.
- His ankle is swollen — he must have sprained it when he fell over.
- You look pale — you must feel sick.
- They are in the waiting room — the doctor must be busy.
The rest of this lesson is in the General English course:
- B — Quick reference
Try it: must, have to, or don't have to?
Choose the best form.
- You ___ see a doctor if the pain gets worse.
(a) must (b) must not (c) don't have to - She ___ take a plaster — the cut is tiny.
(a) must (b) has to (c) doesn't have to - I ___ stay home yesterday because of my flu.
(a) must (b) had to (c) must not - Patients ___ smoke in the hospital.
(a) must not (b) don't have to (c) must
Check your answers in the course — it marks them instantly. This is one of the unit's 4 exercises; the other 3 are in the General English course too.
Practise this unit in the course →