Modals Verbs

Ability Possibility

Can

I can see your house from my bedroom window

Ability Possibility

Could

When I was a child I could run very fast

When I lived in New York I could see the Empire State building from my window

Could vs. Was/were able to Can vs. Be able to

Be able to

We use could for general ability:

He could beat anybody when playing football

We use was/were able to to say that somebody did something in a specific situation:

The fire spread quickly but everybody was able to escape

Can is more informal and usual than be able to.

Be able to can be used in present, past, future, perfect tenses, gerund and infinitive.

I’ll be able to practise my english in London.

I’d like to be able to ski.