In multicomponent media, the equilibrium states are defined by thermodynamic equilibrium conditions in the form of the equalities between the pressures and temperatures of the components, the maximum entropy principle (or the free-energy minimum) for the mixture, and the equality of the velocities of the components. The conservation laws for the components allow for their interaction with each other in the form of forces and energy fluxes containing the differences of the velocities, pressures, and temperatures of the components. The form of momentum and energy exchange between each component and the continuum expressing the collective properties of the ensemble of components, is also considered. It is shown that these momentum and energy fluxes are different from zero only for the states of multicomponent media with velocity nonequilibrium.Key words: equilibrium, multiphase multicomponent medium, interaction of components, closure of the system of equations.Introduction. The great diversity of multicomponent media of natural and man-made origins makes their investigation an extremely difficult problem. Dynamic processes in multicomponent media, accompanied by phase transitions of separate components, are especially complex. The components move at different velocities, which leads to variations in their concentrations in the four-dimensional space x 1 , x 2 , x 3 , t. Because of the interaction of the components, a nonequilibrium multicomponent medium reaches an equilibrium state after a certain relaxation time. The relaxation processes of pressures, temperatures, and velocities in multicomponent media have been studied both for particular mixtures and in general formulations [1][2][3][4][5][6][7]. In these studies, the sum of the functions defining the momentum and energy exchange between all components was usually set equal to zero. This created difficulties in determining the increase in the entropy of multicomponent media during relaxation. Accounting for nonequilibrium kinetic energy partly eliminates these difficulties.Below, we consider problems that arise in the development of models for continuum based on the hypothesis of interacting continua [1]. In these models, the components are structural elements of multicomponent media, which are present simultaneously at each point of the volume. Averaging operations using their characteristics make it possible to pass from the characteristics of the components to the characteristics of a certain continuum, which, like the characteristics of the components, are continuous in the four-dimensional space x 1 , x 2 , x 3 , t. Therefore, they can be described by conservation laws. A continuum whose characteristics are obtained by averaging the corresponding characteristics of the mixture components will be referred to as a virtual continuum. Obviously, one of the conditions of equivalence between multicomponent media and corresponding virtual continua is a macrolevel manifestation of the interaction of components in the multicomponent medium. In other words, the cons...