Quadrilateral

DEFINITION

A polygon bounded by four line segments, each of which can be of any length. The sum of its four angles must be 360?. Types of quadrilaterals include the parallelogram (can be equilateral or non-equilateral), the rectangle (can be equilateral or non-equilateral), the rhombus (always equilateral), the trapezium (non-equilateral), and the trapezoid (non-equilateral). The formula with which to find a quadrilateral's area varies with each type.Also see radial and regular.