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.

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.

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) .

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.