The analytical review presents the thermodynamic properties of zirconium nitride: the phase diagram of the Zr-N system, the homogeneity region, temperature and composition corresponding to congruent melting of ZrN_x, the enthalpy of formation, as well as the electronic structure and chemical bond in zirconium nitride. An equation is given of approximating the temperature dependence for the specific heat crystalline ZrN in the temperature range 298.15-3970 K. The temperature dependences of the specific heat and electrical resistance of liquid zirconium nitride of the composition 0.9ZrN+0.1 ZrO₂ (up to 4500 K), measured by heating with a microseconds current pulse, are presented. The main practical significance of these results lies in the fact that ZrN serves as an inert matrix of mixed nitride fuels (U,Zr)N and (Pu,Zr)N for fast neutron reactors.