From Wikipedia, the free encyclopedia
- henagon (or monogon) – A polygon with one side and one vertex. Impossible to make.
- digon – A polygon with two sides and two vertices. Looks like a straight line (but impossible to do in two dimensions, since both sides overlap).
- Möbius strip – An object that has only one surface. Can be made by cutting a strip of paper, turning it at one end, and pasting it together.
- Klein bottle – Same as a Möbius strip, but in three dimensions. Looks like a bottle, that does not have inside or outside, but only one of them. The Klein bottle is to the Möbius strip what the pyramid is to the triangle.