• Vectors can be represented in terms of basis vectors, a set of vectors that span the vector space

• Mostly will use i, j, k to denote a Cartesian right-handed basis set

• Vector characterised by the 'distance' along the direction of each of a specified set of basis vectors

• The 'distances' are the components of the vector

• Basis vectors usually orthogonal (but need not be). (Ours will be).

• As many basis vectors are required as the dimensionality of the problem; e.g. 3 basis vectors for a 3-D problem

• Basis vectors often but not always constant in space and time