An orbifold is the object obtained by identifying any two points of a map which are equivalent under some symmetry of the map's group.
Orbifold
See also
Orbifold NotationExplore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "Orbifold." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Orbifold.html