contraction

contraction is the short way of writing verb and the word not
example: 

is        +   not  =  isn't 

can     +   not  =  can't
are      +   not  =  aren't 

was     +   not  =  wasn'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