Null vector
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In linear algebra, the null vector or zero vector is the vector (0, 0, …, 0) in Euclidean space, all of whose components are zero. It is usually written 
or 0 or simply 0. A zero vector has no direction, but is orthogonal to all other vectors with the same number of components.
A different kind of vector, also called null vector or zero vector, arises in various generalizations of Euclidean space, as explained below.
Since the word null has a more general (and very different) meaning in computer programming, many programmers prefer the term zero vector to avoid confusion. For example, the statement if ( MyVector == Null ) would intuitively be interpreted as if MyVector is a null pointer by many programmers, as opposed to if MyVector is a null/zero vector.
[edit] Linear algebra
For a general vector space, the zero vector (or null vector) is the uniquely determined vector that is the identity element for vector addition.
The zero vector is unique; if a and b are zero vectors, then a = a + b = b.
The zero vector is a special case of the zero tensor. It is the result of scalar multiplication by the scalar 0.
The preimage of the zero vector under a linear transformation f is called kernel or null space.
A zero space is a linear space whose only element is a zero vector.
The zero vector is, by itself, linearly dependent, and so any set of vectors which includes it is also linearly dependent.
In a normed vector space there is only one vector of norm equal to 0. This is just the zero vector.
[edit] Seminormed vector spaces
In a seminormed vector space there might be more than one vector of norm equal to 0. These vectors are often called null vectors.
[edit] Examples
The light-like vectors of Minkowski space. In general, the coordinate representation of a null vector in Minkowski space contains non-zero values.
In the Verma module of a Lie algebra there are null vectors.
