A $4$NFA is defined as a $5-$tuple M $=($Q$,,\backslash$delta $,$q$0,$F$)$ like an NFA. However, the acceptance is defined differently. An NFA accepts a string w if there is at least one accept state that can be reached from q$0$ while reading the input w$.$ A $4$NFA accepts a string w if at least $4$ accept states can be reached from q$0$ while reading the input w$.$