Can /can't/could / couldn't /be able to

Read the rules / ​Can, could, be able to​​

Can

Is used to talk about possibilities. e.g. ‘Can you meet me at 5?’ Is used to talk about ability. e.g. ‘I can ride a bike’. Is used to make informal requests and orders. e.g. ‘Can you bring me my jumper?’ Has two negative forms, can’t and cannot.

Could

Is used to talk about past abilities. e.g. ‘When I was a child I could do handstands’. Is used to make formal requests. e.g. ‘Could you fax me that document by Tuesday?’

In the negative form, it is  couldn’t.

Be able to

Is sometimes used instead of can or could. Can be used with all tenses. e.g. ‘I will be able to see you next week’.

Is used to talk about short-term ability/ disability . e.g. ‘Are you able to write formal letters?’ Were you able to write when you were three years old?

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