< mathematics > 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 convex symmetric closed surface 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)