MODALS OF OBLIGATION
by Chasses H&M
1. Dont use contracctions with have to
1.1. i have to go. NOT i've to go
2. MUST AND HAVE TO
2.1. Use when we make the rules
2.2. I must get a good nights sleep tonigth
2.3. You have to buy a ticket before you get on the train
3. MUSTN'T, CAN'T AND DON'T HAVE TO
3.1. We use musn't or can't to say that something is not allowed
3.2. We often use mustn't when we make the rules and can't to talk about other people's rules
3.2.1. I mustn't forget to email my mum
3.3. We use don't have to when there is no obligation. It means it's not necesary to do something
3.3.1. I didn't have to call a taxi
4. SHOULD AND OUGHT TO
4.1. We use should or ought to to give advice and recommendations
4.1.1. We should see as much as possible
4.1.2. We ought to see as much possible