## Smooth Manifold

Another word for a (infinitely differentiable) Manifold. A smooth manifold is a Topological Manifold together with its functional structure'' (Bredon 1995) and so differs from a Topological Manifold because the notion of differentiability exists on it. Every smooth manifold is a Topological Manifold, but not necessarily vice versa. (The first nonsmooth Topological Manifold occurs in 4-D.) In 1959, Milnor showed that a 7-D Hypersphere can be made into a smooth manifold in 28 ways.