Modal Verbs (modal auxiliaries)

Can, Could, Be able to


Can and could are modal auxiliary verbs. Be able to is NOT an auxiliary verb (it uses the verb be as a main verb). We include be able to here for convenience.




Can

Can is an auxiliary verb, a modal auxiliary verb. We use can to:

• talk about possibility and ability

• make requests

• ask for or give permission

Structure of Can



The main verb is always the bare infinitive (infinitive without "to").


subject ________ auxiliary verb _________ main verb

+ ___ I _____________ can __________________ play tennis.
- __ He ___________cannot / can't ___________ play tennis.
? __ Can you _____________________________ play tennis?





Notice that:

Can is invariable. There is only one form of can.
The main verb is always the bare infinitive.





Use of Can

can: Possibility and Ability

We use can to talk about what is possible, what we are able or free to do:

She can drive a car.
John can speak Spanish.
I cannot hear you. (I can't hear you.)
Can you hear me?


Normally, we use can for the present. But it is possible to use can when we make present decisions about future ability.

Can you help me with my homework? (present)
Sorry. I'm busy today. But I can help you tomorrow. (future)




can: Requests and Orders

We often use can in a question to ask somebody to do something. This is not a real question - we do not really want to know if the person is able to do something, we want them to do it! The use of can in this way is informal (mainly between friends and family):

Can you make a cup of coffee, please.
Can you put the TV on.
Can you come here a minute.
Can you be quiet!




can: Permission

We sometimes use can to ask or give permission for something:

Can I smoke in this room?
You can't smoke here, but you can smoke in the garden.



(Note that we also use could, may, might for permission. The use of can for permission is informal.)









to be continued