Page "Klein bottle" Paragraph 1

In mathematics, the Klein bottle () is a non-orientable surface, informally, a surface ( a two-dimensional manifold ) in which notions of left and right cannot be consistently defined.

Other related non-orientable objects include the Möbius strip and the real projective plane.

Whereas a Möbius strip is a surface with boundary, a Klein bottle has no boundary.

( For comparison, a sphere is an orientable surface with no boundary.