ADVICE (saying what the best thing to do is)

Shall I (we)?

I (We) can / could

Let’s + bare inf

How about + ing  

Why don’t we + inf

What about + ing

Shall we go to the café?

We could drink a cup of coffee if you like.

Let’s watch TV.

How about going to the cinema tonight.

Why don’t we have some ice cream?

What about playing tennis?

 

 

 

                                                                                                                                                                               

 

 

 

 

 

ADVICE (saying what the best thing to do is)

Should / ought to + present infinitive(it is the best thing to do; I advise you to)

(ought to is sometimes used for advice based on laws, rules, generally accepted ideas)

Shall I? (asking for advice)

had better(it’s a good idea – advice for specific situations)

 

You should do sports to keep fit.

You ought to take care of your pet.

Shall I tell her about my feelings?

You’d better call her.

CRITICISM (saying what the best thing to do in the past was)

Should / ought to + perfect infinitive 

 

You should have taken your little brother to the zoo yesterday.

 

 

 

 

OBLIGATION - NECESSITY

must(it is necessary, I’m obliged – in the present or future when the speaker decides, it borrows the rest of its tenses from have to)

have to (it is necessary, I’m obliged – when others decide for speaker)

have got to(more informal and usual that ‘have to’, it is necessary on a single occasion)

ought to (duty, it’s the right thing to do)

need to + passive infinitiveorneed + -ing form (it’s necessary)

Imust take some medicine. I had to work yesterday.

Did you have to work yesterday?

I have to take some medicine.

I’ve got todo the washing-up.

We ought to take care of nature.

Your hair needs to be cut.

Your hair needs cutting.

ABSENCE OF NECESSITY

needn’t + bare present infinitive / don’t have to / don’t need to(it isn’t necessary in the present or future)

didn’t need to / didn’t have to(it wasn’t necessary in the past and we may not know if it happened or not)

needn’t + bare perfect infinitive(we know that it happened in the past but it wasn’t necessary)

 

You needn’t takethe coat. It isn’t cold.

You don’t have to / don’t need to take the coat.

He didn’t have to buy any milk. We’ve got a lot of it.

She needn’t have cooked dinner. There was a lot of food in the fridge.

PROHIBITION

mustn’t(it’s forbidden)

can’t(you aren’t allowed to)

You mustn’t enter the room.

You can’t take your new bag to school.