Could in present, possibility, probability, logical assumption

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tekken12

New Member
Poland - Polish
Hello everyone, I've been looking for information how to use modal verbs and I found many sources but some of them are in opposite to each other. Maybe some of you native speakers can help me.

I do not understand how to use (can/could) modal verbs of Probability. One source says that Can is used for something that is generally possible, something we know sometimes happens but Can is not used to talk about specific possibilities: He could be on the bus (not: 'can be'). Another source says that I can express possibility in present tense using modal verb Can: She is not here. She can still be at work.

Which one is correct
1. He could be on the bus (not: 'can be')
2. She can still be at work (should be 'could' instead of 'can' as it is a specific possibility?)
Both 1 and 2 seem to be specific possibility that is why I should use 'could' in both examples?
 
  • dojibear

    Senior Member
    English - Northeast US
    Both "could" and "might" fit these two sentences, but "can" does not. Your meaning in both sentences is "it is reasonable to think this is true (right now), but we do not know if it is true or false". We normally use "might be" or "could be" for that.

    "Possibility" has several meanings. Some of them cannot use "can".

    I found a web page talking about "can" as a modal verb (ENGLISH PAGE - Can). It shows modal uses of "can" with several meanings (ability, permission, opportunity, request, possibility). It says the "possibility" use is "usually a generalization or a supposition" and gives these examples:

    Any child can grow up to be President
    Anyone can become rich and famous if they know the right people.
    Learning a language can be a real challenge.
    It can't cost more than a dollar or two.
    You can't be 45! I thought you were about 18 years old.
     

    tekken12

    New Member
    Poland - Polish
    Yes, I know this web site but I do not know if it is correct because in internet there are tons of sites like this one and some of them seem to be in opposite to each other.

    Please watch this youtube movie. First we see how to express possibility in present tense and in 22 seconds of this film the boy is saying "She is not here. She can still be at work."
    For me it is a specific possibility and there should be modal verb 'could' used not can.

    They say in this film that 'can' is 90% certain and 'could' is 50% possibility then we have 'may', 'might' and 'it is likely'.

    So I can use modal verb 'can' as 90% certain, modal 'must' as 100% certain and 'could' as 50% possibility? That is the problem.
     
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