Modals: Can & Could

Use of modal verbs «can» and «could» 

Modal verbs «can» and «could» in positive and negative sentences, questions and short answers 

Types of sentences	Present	Past
+ (Positive)	I/You/She can sing. We/You/They  can sing	I/You/She could sing. We/You/They  could sing
- (Negative)	I/You/She can’t (cannot)sing. We/You/They  can’t (cannot)sing	I/You/She couldn’t sing. We/You/They  couldn’t sing.
? (Questions)	Can You/I/She sing? Can We/You//They sing?	Could You/I/She sing? Could We/You//They sing?
Short answers	- Yes, I/She/We can. - No, I/She/We can’t.	- Yes, I/She/We could. - No, I/She/We couldn’t.

1.1 Use «can» to express the ability or inability to do something in the present (also with the verbs of perception).

Examples

I can swim very well.

They can play the guitar.

She can’t speak any foreign languages. 

I can’t hear you. 

1.2 Use «can» to ask for or give permission in the present.

Examples

Can I use your phone?

You can go home now.

Can we leave early today?

Use «can’t» to decline offers or invitations.

Examples

I can’t come on Friday, I’m afraid.

Sorry, we can’t do it tomorrow.

1.3 Use «could» to express ability or inability in the past.

Examples

When I was a child, I could ride a bike.

She couldn’t read when she was five.

1.4 Use «could» to ask for permission or make suggestion in a polite or formal way.

Examples

Could I borrow your pen?

Could you help me with this?

I could drive you to work.

1.5 Use «can» to describe general truths, possibilities.

Examples

It can get very cold in November.

Traffic can be really bad during rush hour.

It can be hard to find a good job in some areas.

1.6 Use «was(n’t) able to» to talk about whether someone had permission to do something in the past.

Examples

I was able to leave work early.

They weren’t able to go to the concert.