Ch 6
Modals — Obligation and Necessity
Must, have to, need to, and their negative forms.
must / have to
It is necessary.
mustn't
It is not allowed — don't do it!
don't have to
It is not necessary — but you can if you want.
should
It is a good idea (advice, not a rule).
I must remember to call my grandma tonight.
must — the speaker feels it is necessary.
You have to wear a helmet on a motorbike.
have to — a rule from outside (the law).
Do we have to pay to go in?
Questions: usually Do I have to…?
In everyday speech have to is more common than must. Signs and rules often use must: Passengers must show their tickets.
You mustn't use your phone during the exam.
Prohibition — it is not allowed.
You don't have to come to the party if you're tired.
No obligation — you can choose.
We don't have to get up early tomorrow — it's Sunday!
Not necessary.
Past
I had to wait an hour for the bus yesterday.
Past negative
We didn't have to pay — it was free.
Future
You'll have to show your passport at the airport.
Never “musted” or “must yesterday”: use had to.
You must to wear a seat belt.
→
You must wear a seat belt.
no to after must
You mustn't bring food — but you can if you want.
→
You don't have to bring food.
not necessary = don't have to
I must leave early yesterday.
→
I had to leave early yesterday.
past → had to
She don't have to work on Saturdays.
→
She doesn't have to work on Saturdays.
he / she → doesn't have to
Answer with must, have to, mustn't or don't have to.
1
What are three rules at a swimming pool?
2
What do you have to do at home every week?
3
What don't you have to do at the weekend?
4
What did you have to do yesterday?
Recap
must / have to
necessary
You have to wear a helmet.
mustn't
not allowed
You mustn't park here.
don't have to
not necessary
You don't have to pay.
had to
past of must / have to
I had to wait.