In English we use should / shouldn't /ought to / oughtn't to give advice. We use should / ought to to say something is a good thing to do and shouldn't / oughtn't to say something is a bad thing to do.
Example sentences :
Note : To ask for advice we can say: What should I do?
In English, "can" is a modal verb and only has a present, past and conditional form. It can also be used with a future meaning.
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Note : Can is not used to talk about specific possibilities.
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In English, could is used to talk about past ability/ permission/ possibility.
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"Be able to" can be used in the present, past, future, present perfect and as a gerund or infinitive.
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Note : be able to in the present and past is more formal than can or could.
In English we use might or may to say something in the future is possible, but not decided.
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To make questions with might we usually use Do you think...?
Example questions :
In English we can also use might in short answers.
Example short answers :
In English we use have to + infinitive to say something is necessary or obligatory. We normally use have to for a general obligation from an outside source, such as work or the law.
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In English we use don't have to + infinitive to say something is not necessary or obligatory. It means you can if you want to, but it's not necessary.
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To make questions we use do/does.
Example questions :
Form : ( Must + infinitive without to )
In English we use must + infinitive to talk about rules and obligations. We normally use must when the speaker imposes the obligation, such as a teacher to students, or even to yourself.
Form : ( Mustn't + infinitive without to )
In English we use mustn't + infinitive to say something is prohibited.
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Note : You can often use can't or be + not allowed to instead of mustn't.
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Note : Mustn't and don't have to have completely different meanings.
Mustn't Vs Don't Have To
Note : Have to is a normal verb and exists in all tenses whereas must is a modal verb and its only forms are must and mustn't.
You can also use have to and must for strong recommendations.
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In English we use must when we are sure something is true.
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In English we use may or might when we think something is possibly true.
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In English we use can't when we are sure something is impossible.
Examples sentences :
Note : In this context, the opposite of must is can't, NOT mustn't!
In the past, can't, could, may, might and must for probability change to can't have, could have, may have, might have and must have + past participle (Verb 3).
In the past, should and ought to change to should have and ought to have + past participle (Verb 3).
Note : the form of "must" for obligation and "can" are exceptions.
Must for obligation changes to had to + infinitive
Can changes to could or was able to
Modal example sentences | |
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It may help prevent wasting time for both sides. | |
After I finish unpacking my suitcase, we can put them in there. | |
You must be joking! | |
You know what, I can't see any cutlery in the drawer! | |
Mr. Jones, I'm calling about the house in Angel! Can you hear me? | |
I may need to leave him with Mike sometimes. | |
The burglar might like it. | |
We can continue talking about that on the train. | |
I think they should be more understanding. | |
Then we might not be able to find it here, either. | |
It's a very long time, who could stand it? | |
Too bad, they must have understood you are a liar, then. | |
But I wonder what it says, can you show it to me, too? | |
Another big problem is, I can't take Pogo with me. | |
I can try to use as many as I can. | |
Yes, it should be hidden somewhere in the top drawer. | |
But he can't walk on it. | |
But I have to be in Brighton in the afternoon. | |
Umm, yeah, I think we should consider living in Angel, too. | |
I can't promise, but we can try, at least. |