When most people think of shapes, they imagine a triangle, a rectangle, or maybe even a fancier-sounding rhombus or trapezoid. But to mathematicians, shapes encompass a vast universe of surprising ...

A 3D shape with all straight edges and flat faces is a polyhedron. Other 3D shapes with least one curved surface are not polyhedra. A 3D shape with regular polygonal faces, meeting at equal angles, is ...

Two-dimensional (2D) shapes are completely flat. They cannot be picked up. 2D shapes can be found printed in a book or you can draw them on a piece of paper. 2D shapes have sides and corners (also ...