Modal Verbs: CAN/COULD


Modal verbs + infinitive without to (with 2 exceptions: ‘ought to’ and ‘have to’)

No ‘s’ in the 3rd person singular (he might go)

Most modal verbs don’t have tenses (future, past participle…)           

Negative: add ‘not’ to the end of the verbs (I can’t go)

Questions: move the modal verb before the subject (should I tell him?)

CAN/CAN’T (cannot)

  • Something is (not) possible or allowed.
    “We can see the lake from our hotel” (possibility)
    “I’m afraid I can’t go to the party” (impossibility)
    “You’ve just had a sandwich, you can’t be hungry already” (it’s not possible)
    “You can’t smoke here” (you are not allowed)
  • Ability.
     “My grandfather can speak five languages”
  • Suggestion/option.
    “You can call him tomorrow”
  • Sometimes you need to use ‘be able to’.
    “I haven’t been able to sleep recently”
    “I haven’t can sleep recently”

COULD/COULDN’T(could not) Past of ‘can’

  • Present possibilities (we can use ‘could’, ‘might’, or ‘may’ too)
    “They could be brothers. They look so alike!” (I think it’s possible)
    “Your keys might be in the car”
    (I think it’s possible they are in the car)
    “It’s sunny here, but it may be cloudy there”
    (I think it’s possible that it’s cloudy there)
  • Future possibilities (we can use ‘could’, ‘might’, or ‘may’ too)
    “It could cost more than you expect” – I think it’s possible that it will cost more than you expect.
    “You might miss the train unless you leave now” – I think it’s possible that you will miss the train if you don’t leave now.
    “I may be a bit late” – I think it’s possible that I’ll be a bit late
  • Past general ability or permission to do something.
    “My grandfather could speak five languages” (general ability)
    “We could do whatever we wanted” (we were allowed to do)

If you want to say that somebody did something in a specific situation, use ‘was/were able to’ or ‘managed to

“There was nobody to disturb me so I was able to finish my work”
“There was a fire in the building but everybody managed to/was able to escape”

Compare these two sentences:
“Nadal was an excellent tennis player. He could beat anybody” – he had the general ability to beat anybody.
“Nadal and Federer played a match yesterday. Federer played well, but Nadal managed to beat him” – he managed to beat him this time.

  • Used to talk about possible actions now or in the future (especially to make suggestions).
    “We could go to the cinema tonight” (‘can’ is also possible. ‘Could’ is less sure than ‘can’)
    “They could come with us” (‘can’ is also possible. ‘Could’ is less sure than ‘can’)
  • Used for actions that are not realistic.
    “I’m so hungry, I could eat a horse” (unrealistic)
    “I could run 10k if I trained” (possible, but less sure)
    “This is a fantastic place. I could stay here forever”
  • Used to say that something is (im)possible now or in the future.
    “The story could be true, but I don’t think it is” (present)
    “They are on their way. They could arrive at any time”
    “They could be here”
    “They couldn’t be here”

Compare these two sentences:
“The weather can change very quickly in the mountains” (in general)
“The weather is nice, but it could change”
(the weather now)

  • Could (not) have + past participle = used to talk about the past.
    “I was so tired, I could have slept for a week”
    “We couldn’t have found the place without a map”
    “We had a really good holiday. It couldn’t have been better”
  • Polite question.
    “Could I call you later?
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