Norm
From Glossary
This is a function of a vector, say that satisfies three properties:
 Homogeneous:
 Positive: (Note: by homogeneity, so is the unique vector with zero norm.)
 Subadditive:
Norms that arise frequently in mathematical programming are:

Euclidean norm (on ):
L_inf (on ):
L_p
Matrix norm (induced by vector norm):
Supremum norm (on function space):