In this paper, we strictly establish classical concepts and relations according to a Dirac equation with scalar, vector, and nonlinear potentials. To calculate classical parameters for a moving spinor, the local Lorentz transformations for parameters are derived. The calculation shows that different kinds of potential result in different energy-speed relations, and the energy-speed relations for each potential are derived in detail. The usual mass-energy relation E = mc 2 holds only for the linear spinor. The energy-speed relations can be used as fingerprints to identify the interactive potentials of a particle by elaborated experiments. The analysis and results of this paper can also provide some natural explanations for the foundation of quantum mechanics, and clarify some... long-standing puzzles in the theory.