The coefficient of electric conductivity of some substances is studied; peculiarities of the general character are outlined in the process of the description. For generalization of the kinetic characteristics in solids, the factors of reciprocity determining the level of interband exchange and allowing presentation of the kinetic characteristics of metals, semimetals, and semiconductors from one point of view are introduced. The technique of the description taking into account the interband exchange and the presence of common electrons in the longrange order of their interaction is developed. In particular, there are obtained analytical expressions for generalized electric conductivity coefficients, the Hall coefficient, and the thermopower, which permit description of these characteristics in metals, semimetals, and semiconductors using unique formulae. The peculiarities in the description of the electric conductivity coefficient for unordered structures and conductors of nonelectron type are found. There are presented common approaches in the description of various liquids by means of defining of the effective charge characteristic by analogy with the description of free quasiparticles in solids by the effective mass method. The effective charge of an arbitrary current carrier in liquids is determined by means of a transference number expressed through the ion radii and masses of the charge carriers, and it can be overdetermined up to the change of the charge sign.