example:
is + not = isn't
can + not = can't
are + not = aren't
are + not = aren't
was + not = wasn't
do + not = don't
does + not = doesn't
have + not = haven't
do + not = don't
does + not = doesn't
have + not = haven't
shall + not = shan't
will + not = won't
must + not = mustn't
were + not = weren't
will + not = won't
must + not = mustn't
were + not = weren't