Modal Verbs: must, have to, should កិរិយាពិសេស must, have to, should

We can use both must and have to to talk about obligations: things we cannot choose not to do. -We must talk to her before she leaves. -I have to go into work early tomorrow. The obligation with must is more personal. -I must pay him back like I promised. The obligation with have to is more situational. -He has to do a lot of work every week. It is rare to use must to talk about obligations in spoken English. However, we can use must to talk about obligations in formal and written English. -All passengers must have a valid ticket. -Candidates must arrive no later than five minutes before the scheduled start time. We use mustn’t to talk about prohibitions: things we are not allowed to do. -Visitors must not touch the paintings. -Passengers must not talk to the driver while the bus is moving. We use ‘don’t have to’ to talk about something that is not necessary. We can choose to do it or not. -You don’t have to be here before ten. -She doesn’t have to finish it today. Like must, mustn’t is more common in formal or written English. In spoken English it’s more common to use can’t. +You may see a sign saying: -Mobile phones must not be used while driving. +But, if we’re talking, we’d probably say: You can’t use your mobile phone while driving. We use should to give advice or express our opinions. -You should go to bed early. Then you wouldn’t feel so tired all the time. -He should do more work if he wants to get promoted. We can’t use should to talk about obligations or rules. However, we can also use must or have to to give advice. -You must try the fish. It’s delicious! -You have to try the fish. It’s delicious! If we want to give negative advice, only shouldn’t is possible. We can’t use mustn’t or don’t have to. -You shouldn’t eat so much chocolate at once. You’ll make yourself sick. -You shouldn’t take the job unless you’re sure it’s what you want.