The Concept of Temperature in the Modern Physics

The physical quantity "temperature" is a cornerstone of thermodynamics and statistical physics. But it is necessary to mention that very frequently the scientists forget about the conditions to be satisfied in order to introduce "temperature" in macroscopic physics. In the present paper the short introduction to the classical concept of temperature for macroscopic equilibrium systems will be given. The concept of "spin temperature" in condensed matter physics will be reviewed and the advantages of thermodynamic approach to the problems of magnetism will be illustrated. Finally, the concept of temperature will be discussed regarding the nanoscale physics and non-extensive systems.