We derive generic equations for a vector field driving the evolution of a flat homogeneous isotropic universe and give a comparison with scalar field dynamics in cosmology. Two exact solutions are shown as examples, which can serve to describe inflation and a slow decrease of dynamical'cosmological constant'as given by the scalar quintessence. An attractive feature of the vector field description is the generation of'induced mass' proportional to the Hubble constant, which results in a dynamical suppression of actual cosmological constant during the evolution.