S> A real-valued function modelling the length of a vector. The norm muSt be homogeneouS and Symmetric and fulfil the following condition: the ShorteSt way to reach a point iS to go Straight toward it. Every convexSymmetric cloSedSurface Surrounding point 0 introduceS a norm by meanS of MinkowSki functional all vectorS that end on the Surface have the Same norm then. The moSt popular norm iS the Euclidean norm. (2004-02-15)