Temperature is a physical property of a material that gives a measure of the average kinetic energy of the molecular movement in an object or a system. Temperature can be defined as a condition of a body by virtue of which heat is transferred from one system to another. It is pertinent to mention here that both temperature and heat are different.
Temperature is a measure of the internal energy of a system, whereas heat is a measure of the transfer of energy from one system to another. Heat transfer takes place from a body at a higher temperature to one at a lower temperature. The two bodies are said to be in thermal equilibrium when both of them are at the same temperature and no heat transfer takes place between them. The rise in temperature of a body is due to greater absorption of heat, which increases the movement of the molecules within the body.
The temperature is an intensive physical quantity, and this means that to be defined conceptually it needs evaluation in terms of effects caused by its variations on the behavior of the materials. In fact, the temperature is evaluated as a function of the average kinetic energy possessed by the atoms constituting the matter and describes the thermodynamic state of the systems in equilibrium.
Furthermore, once the unit of measurement has been defined, it is not possible to define a multiple or sub-multiple quantity; since the temperature is an intensive quantity, by putting two bodies of unitary temperature in contact, the set consisting of the two bodies still has a unitary value. It will, therefore, be necessary to define not only the unitary quantity but also each multiple and sub-multiple thereof, that is, to define a thermometric scale.