Definition:Vector Space

Definition
Let $\left({K, +_K, \times_K}\right)$ be a division ring.

Let $\left({G, +_G}\right)$ be an abelian group.

Let $\left({G, +_G, \circ}\right)_K$ be a unitary $K$-module.

Then $\left({G, +_G, \circ}\right)_K$ is a vector space over $K$ or a $K$-vector space.

That is, a vector space is a unitary module whose scalar ring is a division ring.

If $\times_K$ is commutative, then $\left({K, +_K, \times_K}\right)$ is by definition a field.

In that case, the scalar ring of $\left({G, +_G, \circ}\right)_K$ is called the scalar field of $\left({G, +_G, \circ}\right)_K$.

Comment
Some sources insist that $\left({K, +_K, \times_K}\right)$ needs to be a field, not just a a division ring, for this definition to be valid.

As a vector space is also a unitary module, all the results which apply to modules, and to unitary modules, also apply to vector spaces.

Linear Space
A vector space is also sometimes called a linear space, especially when discussing the real vector space $\R^n$.

Also see

 * Scalar Field