系动词be、助动词、情态动词的否定形式一般可以缩写成为一种简略的形式。如：

is not―isn’t                                are not―aren’t

was not―wasn’t                         were not―weren’t

has not―hasn’t                           have not―haven’t

will not―won’t                           would not―wouldn’t

shall not―shan’t                         should not―shouldn’t

do not―don’t                              did not―didn’t

ought not―oughtn’t                     dare not―daren’t

used not to―usedn’t / didn’t use to