A quadrilateral in which only one pair of opposite sides is parallel is called a .

A rectangle is a quadrilateral in which both diagonals are equal and they bisect each other.

A parallelogram is a rectangle.

Every parallelogram is a rhombus.

A square is the only quadrilateral in which all sides and angles are equal.

A decagon is a polygon with eight sides.

A heptagon is a polygon with seven sides.

If all the sides and angles of a polygon are equal, it is called an irregular polygon.