direction (of a vector)

is: a characteristic property of a vector which determines its orientation with respect to a system of coordinates. [P2.2]

usually is specified: in two dimensions relative to a two-dimensional Cartesian coordinate system, by quoting the angle (measured in the anticlockwise sense) from the positive -axis to the vector. [P2.2]

may be more generally specified: by expressing the vector in terms of its components relative to a given Cartesian coordinate system.

See scalars and vectors in the Maths handbook.