Quadrilaterals are one of the most complex sets of polygons. In this topic, you reviewed the properties of six different sets of quadrilaterals – parallelograms, rectangles, rhombi, squares, trapezoids, and isosceles trapezoids. The quadrilaterals in this module can be grouped into two broader categories, those with two sets of parallel sides and those with one set of parallel lines. More importantly, you learned to apply these problems in real life settings and situations.