Euler characteristic

The Euler characteristic of a shape is a number that describes a topological space, so that anything in the space will have the same number. It is calculated by taking the number of points in the shape, the number of lines in the shape, and the number of faces of the shape. Then, you find the Euler characteristic with this formula:

$\chi =V-E+F\,\!$

V is the point count, E the line count, and F the amount of faces. For most common shapes, the Euler Characteristic is 2.

Name	Image	Vertices (Points) V	Edges (Lines) E	Faces F	Euler characteristic: V − E + F
Tetrahedron		4	6	4	2
Hexahedron or cube		8	12	6	2
Octahedron		6	12	8	2
Dodecahedron		20	30	12	2
Icosahedron		12	30	20	2