In mathematics, the norm of a vector is its length. A vector is a mathematical object that has a size, called the magnitude, and a direction. For the real numbers, the only norm is the absolute value. For spaces with more dimensions, the norm can be any function with the following three properties:
The most common usage of this is the Euclidean norm, also called the standard distance formula.
- The one-norm is the sum of absolute values:  This is like finding the distance from one place on a grid to another by summing together the distances in all directions the grid goes; see Manhattan Distance.
- Euclidean norm (also called L2-norm) is the sum of the squares of the values:
- Maximum norm is the maximum absolute value:
- When applied to matrices, the Euclidean norm is referred to as the Frobenius norm.
- L0 norm is the number of non-zero elements present in a vector.