2D shapes are two-dimensional objects that have only two dimensions—width and length—and no depth. 2D shapes can be drawn on a piece of paper and do not have thickness like 3D shapes. Examples of common 2D shapes include circles, squares, rectangles, triangles, ovals, and polygons like pentagons, hexagons, and octagons. Each shape is made up of a collection of sides and angles, which are determined by measuring perimeter (outer distance of the shape) and area (interior space of the shape).