request, instruction

e.g. Can you switch on the light for me? capability

e.g. The summers in England can be really unpredictable. with be to make criticisms

e.g. Susan can be a real pain in the neck at times. ability

e.g. I can't come to the game on Friday. when you feel sure something is not possible (opposite of must)

e.g. The tennis match can't be over yet. (I'm sure it isn't). possibility or uncertainty (can also use might)

e.g. He could be the one for you! request (more polite than can)

e.g. Could you switch on the light for me? suggestion

e.g. We could go on a picnic this afternoon. asking for and giving permission

e.g. "Could I use your phone?"

"Yes, of course you can" unwillingness

e.g. I couldn't possibly leave Tom alone while he's in this state. with comparative adjectives to express possibility or impossibility

e.g. I could be fitter.

e.g. He couldn't study harder. strong advice (less used than should)

e.g. You'd better do the washing up now.

e.g. I'd better not go out tonight, because I have to get up early tomorrow.