  The complete explicitly covariant 4-dimensional description of the dynamics
of a free classical particle with spin within the framework of the special
relativity theory is presented. The key point of our approach is the the
introduction of the new vector field which enables to define the analogues of
the mean spin and position variables. The supplementary conditions are
discussed and it is demonstrated that the Frenkel condition unambiguously
determines the dynamics of a spinning particle.
