<p>Deformation and fracture of structural materials reflect several complex physical and thermodynamic processes that occur sequentially and simultaneously in the material at the micro and macro levels. In a material, as in any thermodynamic system, there are continuous transformations of various types of energy. The emergence of new physical models of deformation and the idea of the hierarchy of fracture processes make it possible to adjust the known approaches and encourage a modern view of the strength of materials as a loss of local and overall stability of a thermodynamic system. Many physical and phenomenological studies aim to find the energy criteria of fracture. The physical and phenomenological principles of energy criteria for the fracture of a continuous medium under different deformation mechanisms are formulated: at evaporation, melting, single and multiple loading. A general relative thermodynamic criterion for the fracture of materials is proposed. The criterion relates the fracture work to the internal energy of the material. The deformation mechanism determines its numerical value and remains constant for thermodynamically similar materials. The physical meaning of the criterion is established. At the macro level, it reflects the relationship between the fracture work and the thermal deformation energy and outlines the limit of possible growth of the body volume due to deformation, and at the micro level, it determines the theoretical strength and the distance to the termination of interatomic interaction. The fundamentality and universality of the criterion are confirmed by the known phenomenological dependencies of the limit state, which can be considered as its special cases.</p>