A surface which is homeomorphic to a finite collection of spheres, each with a finite number of handles, cross-handles, cross-caps, and perforations. A preliminary version of the classification theorem of surfaces states that every surface is ordinary.
Ordinary Surface
Explore with Wolfram|Alpha
References
Francis, G. K. and Weeks, J. R. "Conway's ZIP Proof." Amer. Math. Monthly 106, 393-399, 1999.Referenced on Wolfram|Alpha
Ordinary SurfaceCite this as:
Weisstein, Eric W. "Ordinary Surface." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/OrdinarySurface.html