A quantity which has magnitude and has some sense of direction is called Vector. For example, force, velocity, acceleration. If a is a vector quantity, it can be represented as or or in bold a . Magnitude of a vector is a positive quantity and is represented as or simply a. Geometrically, vectors are represented by directed line segments i.e. (by arrows). Length of the arrow represents the magnitude of the vector and the direction of the arrow represents the direction of the vector.