The Opposite Sides Parallel and Congruent Theorem states that if a quadrilateral has a pair of opposite sides that are parallel and congruent, then the quadrilateral is a parallelogram.
If it doesn't have parallel sides, it's just classified as a quadrilateral.
Then, the opposite sides are congruent.
I would be seriously concerned if a quadrilateral had more than two pairs of opposite sides parallel! A quadrilateral with two pairs of opposite sides parallel is a parallelogram.
A Trapezium (can have two opposite sides parallel)A kite has no parallel opposite sides
A quadrilateral is a polygon with four sides. A parallelogram is a quadrilateral in which the opposite sides are parallel.
A square's opposite sides are parallel and all the sides are congruent.
A parallelogram is a quadrilateral with opposite sides that are parallel.