manifold (idea)

(see all of manifold, there are 4 more in this node)

A few examples of manifolds:

R^n
The region in the plane lying between a collection of nonintersecting smooth simple closed curves.
The unit 2-sphere x^2+y^2+z^2=1 in R^3.
The region in 3-space lying between a collection of nonintersecting smooth surfaces.
The Mobius strip.