It is established that, in a general case, the equations of state of a real gas are identical to the constitutive equations of cubic strain of a deformable material. Based on this, we use the fundamental notion of deformation mechanics of the division of strain into free and elastic strain. As a result, we reduce the equation of cubic strain to the form of a generalization of the ideal gas law. We establish specific features of the gaseous state as compared with the solid and liquid states. In particular, the continuum physical meaning of an ideal gas and the universal gas constant is revealed. We construct two-parameter expressions for the compressibility coefficient for an arbitrary state of aggregation, which reveal the physical meaning of the corresponding experimental data and agree with the notions of the molecularkinetic theory of gases.