Named for Plato, who theorized that the classical elements were made of these regular polyhedrons, three of the Platonic solids are composed of equilateral triangles: the tetrahedron, octahedron, and ...

Two-dimensional (2D) shapes are completely flat. They cannot be picked up. A polygon is a 2D shape with straight sides that meet at vertices. Polygons have names that show the number of sides they ...

Complete this interactive activity to find out more about 3D shapes and then put your knowledge to the test. Cubes have 6 flat faces which are all the same size. Everyday things that have the shape of ...