In geometry, a rectilinear figure can be defined as a plane figure or shape all of whose sides meet at right angles. A Rectilinear polygon is a polygon all of whose edge intersections are at right angles. Thus the interior angle at each vertex is either 90 degree or 270 degree. Rectilinear polygons are a particular case of isothetic polygons. Rectilinear polygons are also known as orthogonal polygons. A figure formed by straight lines only is called a rectilinear figure. It is a plane figure bounded by line segments. Rectilinear means along a straight line or in a straight line or forming a straight line. The chapter discusses different properties and theorems related to quadrilaterals like squares, parallelograms, trapezium, rectangle etc.