A parallelogram is a quadrilateral that has four parallel sides. Some of its properties include having opposite sides that are equal in length, opposite angles that are congruent and diagonals that cut a cross and bisect each other.
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A parallelogram is a quadrilateral (4 sided figure) in which the sides opposite each other are parallel and equal in length. Some examples would be a square or a rectangle. You can find more information here: http://www.mathopenref.com/parallelogram.html