Modal verbs to express ability

We use the modal verbs can, could and be able to + verb infinitive to talk about ability.
Here’s an overview, with examples:

Modal verbs to express ability
present past
can
We use can when we speak about general ability in the present.
could
We use could when we speak about general ability in the past.
Tommy can swim.
I can play the guitar. Can you play?
Picasso could paint when he was two.
I could swim before I could walk.
The negative of can is can't (cannot):
I can't ski and I can't skate.
The negative of could is couldn't (could not):
I couldn't swim until I was ten.
We also use can to speak about specific situations in the present:

I can hear you, but I can't see you.
Can you hear me? ∼ Yes, I can.
We often use was able to to speak about about a specific situation in the past:

We fixed the car and then we were able to drive home.
We prefer could to speak about a specific situation in the past when we use these verbs: see, hear, feel, smell, taste, remember, believe, understand, decide.

They could smell smoke.
I could understand him perfectly.
Questions about ability in the present:
How many languages can you speak?
Can you name all the capitals of Europe?
Questions about ability in the past:
Could you write before you started school?
Could you ride a bike when you were small?


See also: Can, can’t, could, may: modal verbs for permission >>