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Can, Could, Be able to, Be allowed to - Coggle Diagram

- - - - when we talk about sth that is happening as we speak
        
        Watch me, Mum! I can stand on one leg. (not I'm able to)
        
        before passives
        
        CDs can now be copied easily. (not are now able to)
        
        when the meaning is "know how to"
        
        Can you cook? (not Are you able to)
  - - - She swam strongly and was able to cross the river easily. (not could cross)
  - - - I tried to get up but I couldn't move. (rather than I wasn't able to)
    - - I could remember the crash but nothing after that. (rather than I was able to remember)
    - - All we could see were his feet. (rather than All we were able to see)
    - - I could nearly touch the celling. (rather than I was nearly able to touch)
- - - - theoretical possibility
        
        It could be expensive to keep a cat. (if we had one, it could or it may not be expensive)
    - - when sth is possible and actually happens
        
        It can be expensive to keep a cat. (it can and sometimes it is)
    - - when sth is theoretically or actually impossible
        
        There can't be many people in the world who haven't watched television.
        
        The doctor can't see you this morning.
    - - where there is a very real possibility of a future event happening
        
        W can stau with Jim in Oslo. (we will be able to stay)
    - - to suggest that sth is less likely or there is some doubt
        
        We could stay with Jim in Oslo. (it's posible if he's there)
- - - - for general permission in the past
        
        Anyone could fish in the lake when the council owned it.
        
        Anyone was allowed to fish in the lake when the council owned it.
    - - one-off permission
        
        Although we didn't haver a ticket, Ken was allowed to come in. (not could come in)
      - in negative sentences both are ok
        
        We weren't allowed to open the presents until Chrismas morning.
        
        We couldn't open the presents until Chrismas morning.
- - - - You could have taken a taxi from the airport. (but you didn't)
        
        why not could alone?
  - - - can have + past participle
        
        He can have fotgotten about me.
      - can have + past participle
        
        questions
        
        Can he have forgotten about our appointment?
        
        negations
        
        I can’t have lost my keys again!
        
        negating words
        (barely, hardly, only, or never)
        
        I can hardly have been responsible for your losing your keys.
        
        with subordinate clouse
        
        I don't believe he can have forgotten about me.