出典:Wiktionary
Euler characteristic (複数形 Euler characteristics)
出典:Wikipedia
出典:『Wikipedia』 (2011/06/14 14:46 UTC 版)
In mathematics, and more specifically in algebraic topology and polyhedral combinatorics, the Euler characteristic (or Euler–Poincaré characteristic) is a topological invariant, a number that describes a topological space's shape or structure regardless of the way it is bent. It is commonly denoted by χ (Greek letter chi).