Can one say

a. You can not do it now and do it later.

b. You may not do it now and do it later.

(Meaning: You can do it later. You don't have to do it now.) ?

Can one say c. It could happen and it could not happen.

(Meaning: It might happen and it might not happen.) ?

My feeling is that (a) works and (b) and (c) do not. For (a) to work 'can' has to be accentuated. It will still be a somewhat strange sentence, I think, but it will work. (Can you not speak for a few minutes?)

That is my take on it, but I am not sure at all. Or else, I wouldn't be asking!

Many thanks.

  • It's not clear what you're actually trying to express with these different options. Can you edit your question to include this? Commented Apr 7, 2016 at 10:05

2 Answers 2


"You can not do it now and do it later." means (to me at least) "It's not possible to do it now and also do it later": like the expression "You can't have your cake and eat it", which would be better worded as "You can't eat your cake and still have it".

"You may not do it now and do it later." means the same as the above, with the exception being that "may" has a slight implication that the reason you can't do it is that you're not permitted to, rather than it being actually impossible.

Neither of them mean "You don't have to do it now". For this I would write "You can do it now, or later." (if i was trying to be as terse as possible)

For your second question, you could just say "It might happen" or "It might not happen". Each of these states that there are two possibilities - it happening, and it not happening - but implies that one of the cases is more likely: "It might happen" is like saying "It is more likely that it won't happen", and conversely saying "It might not happen" is like saying "It is more likely that it will happen". "Might" here implies a small probability.

To say "It could not happen" is totally different: this means that it is impossible. Somewhat inconsistently, however, to say "It could happen" means the same as saying "It might happen".


The morpheme for 'not' usually applies to the verb, no matter where it appears in the verb phrase, and even if a modal auxiliary (like 'will') is used. This is not true when using the modal 'can' (which expresses possibility). Instead of having a separate modal for impossibility, we make do by negating the possibility. This requires us to use nuance when trying to negate the verb instead of the modal ('I can NOT go' vs 'I can't go').

  • Thank you all so much. The issue Aml raises is exactly the thing I am after! Could one ever say: 'You can NOT do it now and do it later.' and 'It could happen and it could NOT happen.' with the meanings I have provided. It is true that normally those sentences have other meanings which are not the desired ones. Many thanks.
    – azz
    Commented Apr 7, 2016 at 20:46

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