A quadrilateral is a geometric shape that is composed of 4 sides (sometimes called edges) and 4 corners (sometimes called vertices). All the four sides in a quadrilateral shape may or may have the same length. Consequently, all corners may vary in terms of angles, but will always total to 360 degrees.

There are many different types of quadrilateral shapes. Some are classified into simple and complex quadrilateral types. Simple quadrilaterals are those that have sides that do not intersect or cross with each other. Complex quadrilaterals are shapes that involve crossing of lines or sides. A basic example of a simple quadrilateral is a square. A bowtie shape meanwhile is an example of a crossed or complex quadrilateral.

Simple quadrilaterals may also be classified as concave and convex, depending on the shape and the angles involved. Various parallelograms are classic examples of simple and convex quadrilaterals. A parallelogram consists of 2 sets of parallel edges or sides. This means that opposing edges or sides are parallel to each other and have the same length. And because of this side placement, the angles that are opposite each other are also equal in size. A square is the most regular parallelogram that people are familiar of and it consists of all four sides having the same length. All four angles are also the same at 90 degrees. Another example of a convex parallelogram is a rectangle. Similar to a square, all four angles measure 90 degrees but not all sides have the same length. In a rectangle, two sets of parallel sides are of the same length. Other convex quadrilaterals are the rhombus, rhomboid, kite, trapezoid, cyclic quadrilateral, and tangential quadrilateral among others. A dart or an arrowhead, more commonly known as a geometric chevron shape, is an example of a concave type of quadrilateral.