1. OBLIGATION: MUST HAVE TO SHOULD

2. PRESENT/ FUTUREPASTEXAMPLES MUST: Subject+ must + verb _______ (past obligation is expressed with had to) You must go now. I must call my sister tomorrow. HAVE TO (external): Subject + have to + verb HAD TO: Subject + had to + verb Children have to go to school. I had to work on New Year’s Eve. SHOULD: Subject + should + verb (Should is weaker than must/have to. It is used to give advice to someone or to say that something is a good idea) SHOULD HAVE + Past participle: Subject + should + have + past participle (to express unfulfilled past obligation) You should tell them the truth. You should have told them the truth.

3. PROHIBITION: MUSTN’T ABSENCE OF OBLIGATION “IT’S NOT NECESSARY”: DON’T HAVE TO

4. PRESENT / FUTURE PASTEXAMPLES MUSTN’T: Subject + mustn’t + verb (to express something that’s not allowed or permitted) CAN’T (external): Subject + can’t + verb ___________ (past prohibition is expressed with was/were not allowed or COULDN’T Subject + couldn’t + verb I mustn’t eat so much sugar. You mustn’t park your car outside the shop. I was not allowed to/ couldn’t park outside the shop. DON’T HAVE TO: Subject + don’t/doesn’t have to + verb (means that something is not necessary, but you can do it if you want to) DIDN’T HAVE TO: Subject + didn’t have to + verb You don’t have to come to class tomorrow. I didn’t have to wear a uniform at school.