1. CAN and COULD

Can

Can is used to express ability , possibility , permission and more.

Examples:

  • The boy  can ride a horse faster than his father can. (Ability)
  • You  can  get into trouble for smiling at every girl. (Possibility)
  • You  can  finish the whole bowl of chicken soup if you like. (Permission)
  • Can I help you to count the money? (Offer) 
  • Can you not sing at all? (Request)
  • You can  lie down on the couch even if you are not tired. (Suggestion) 

Using '( be ) able to' in place of ' can'

Sometimes the phrase ( be )  able to  can be used in place of  can  when it is necessary.

Examples:

  • I  can  finish it in two days. = I  am able to  finish it in two days.
  • We  can  swim across the river.  = We  are able to  swim across the river.  Â

Could

Could  is a more polite form of can  when used to make a request. The modal  could  can be used to express the following. Â

Examples:

  • Years ago, he could dive from the diving board up there. (Past tense of can )
  • Could you feed my goldfish while I’m away? (Polite request) 
  • She could be making the wrong decision in divorcing him. (Possibility)
  • My grandfather  could  speak six languages including Swahili. (Ability)
  • Could I bring my puppy along? (Permission)

  • You could warn him to leave you alone, or you could keep a bodyguard. (Suggestion)

Can/could  is used with infinitive without to .

Examples:

  • We can  fly  kites today.
    Not : We can to  fly  kites today.
  • You could be making  a big mistake.
    Not : You could to be making a big mistake.

The suffix  –s  is not added whether to the modal verb or the main verb  in the third person singular .

Examples:

  • She can  dance the tango.
    Not : She cans  dance the tango.
    Not : She can dances  the tango.

Could  is often used together with the perfect tense  (Could + perfect tense) . Â

Examples:

  • You  could have avoided  the fight by not using the word ‘stupid’.
  • He  could have come along if he wanted to.
  • The home team  could have won  the match by not committing so many fouls.
  • I  couldn’t have known  if no one told me about it.
  • We  couldn’t have got it right without the map.

Could  can be used to not really mean what is said.

Examples:

  • I am so hungry, I could  eat a whole turkey.
    Not : I am so hungry; I can  eat a whole turkey.
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