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.

**References**

Bredon, G. E. *Topology & Geometry.* New York: Springer-Verlag, p. 69, 1995.

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1999-05-26