can, could, be able to
Use can and be able to to say that someone has the ability to do something. Be able to is more formal
• Can you swim?
• Young children are not able to open the bottle.
Use could to say that someone has the ability to do something, but does not do it
• He could do a lot better.
Could is also the past form of can. Use could or a past form of be able to to say that someone had the ability to do something in the past
• She could ride a bike when she was three.
• He was able to walk with a stick.
!! In the following cases, you cannot use can. You must use be able to:
with used to, to say that someone had the ability to do something in the past but no longer does
• I used to be able to play the violin.
to talk about future ability. Use will be able to
• After only a few lessons, you will be able to understand basic Spanish.
after other verbs, for example might, may, would, want, or hope
• He might be able to fix your car.
• You should be able to taste the difference.
• I want her to be able to use a computer.