Negative short forms

isn’t = is not
wasn’t = was not
aren’t = are not
weren’t = were not

don’t = do not
doesn’t = does not
didn’t = did not

haven’t = have not
hasn’t = has not
hadn’t = had not

can’t = cannot (written as one word)
couldn’t =could not
won’t = will not
wouldn’t = wouldn’t
mustn’t = must not
shouldn’t = should not

not used anymore:

shan’t = shall not
(although it may exist in some regions)

Semi-modals ‘dare’ (oser) and ‘need’ (avoir besoin) can also take negative short forms, but are less common today:

daren’t = dare not ‘I’d like to, but I daren’t ask him’
needn’t = need not ‘you needn’t take an umbrella, it’s not going to rain this afternoon’