A line segment that connects two non-consecutive vertices is a diagonal in a polygon. Every quadrilateral has two of these diagonals, which separate it into triangles.
A quadrilateral is a polygon that has four sides. The sum of the interior angles in a quadrilateral is 360 degrees. There are many types of quadrilaterals, including the square, rectangle, rhombus, trapezoid and parallelogram. A rectangle is a quadrilateral with four right angles, while a square also has four right angles but also has four equal sides. A parallelogram has opposite sides that are parallel, while a trapezoid has one pair of parallel sides. A rhombus has four equal sides.