A$/$An entity may be used in the place of a many$-$to$-$many relationship $($e$.$g$.$ enrollment$),$ especially when there are attributes that belong to the relationship $($e$.$g$.$ grade$)$ rather than to either of the entities participating in the relationship $($e$.$g$.$ student, class$).$

associative $($or composite$)$

weak

categorization

subjective