What is a Quadrilateral A closed figure bounded by four line segments is called a quadrilateral. All closed figures shown in figure are quadrilaterals as all of them have four line segments. A quadrilateral has four sides, four vertices, and four angles. Let us consider a quadrilateral PQRS.Sides of the quadrilateral PQRS are PQ, QR, RS, SP, or QP, PS, SR, RQ. … [Read more...] about What is a Quadrilateral