What Is a 4-Sided Polygon Called?

Quadrilaterals are considered simple if no self-intersections occur, or complex if self-intersection does occur. Depending on the shape, simple quadrilaterals are termed either concave or convex. Simple quadrilaterals have interior angles whose sum equals 360 degrees of arc, while complex quadrilaterals have a total of 720 degrees of arc when all four angels on both sides of the intersection are combined.