Basis
A basis of a vector space is a linearly independent set of vectors that spans . Every vector in can be written uniquely as a linear combination of basis vectors.
Every vector space has a basis (this requires the axiom of choice for infinite-dimensional spaces). All bases of a given vector space have the same cardinality, called the dimension of .
The choice of basis determines the matrix representation of linear maps. Changing the basis changes the matrix but not the underlying map.