1) four sides, four vertices
2) The sum of interior angles is 360 degrees.
3) with two diagonals that intersect each other
1) Parallelogram has two pairs of opposite parallel sides; trapezoid has only one pair of opposite parallel sides.
2) Parallelogram's diagonals are always congruent, trapezoids diagonals are sometimes congruent.
3) The diagonals of parallelogram bisect each other; trapezoid's diagonals do not bisect each other.
4) The opposite angles of parallelogram are always congruent; Trapezoid's opposite angles are never congruent.