a quadrilateral in which both pairs of opposite sides are parallel.
a parallelogram in which at least one angle is a right angle.
a parallelogram in which at least two consecutive sides are congruent.
a quadrilateral in which two disjoint pairs of consecutive sides are congruent.
a parallelogram that is both a rectangle and a rhombus.
a quadrilateral with exactly one pair of parallel sides (The parallel sides are called bases of the trapezoid).
a trapezoid in which the nonparallel sides are congruent