Modal verbs (Can)

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.

In this lesson we look at these three verbs, followed by a quiz to check your understanding:

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

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

	subject	auxiliary verb	main verb
+	I	can	play	tennis.
-	He	cannot	play	tennis.
		can't
?	Can	you	play	tennis?

Notice that:

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

The main verb is always the bare infinitive (infinitive without "to"). We cannot say:

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.

1. Can you help me with my homework? (present)
2. 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:
   
   1. Can I smoke in this room?
   2. 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.)