Heat

In thermodynamics, heat is defined as energy in transfer between a body and its surroundings, other than through thermodynamic work or through transfer of matter. In the process of transfer, heat is not necessarily conserved, but can be generated by friction. In thermodynamics, temperature is defined in macroscopic terms, through the concepts of heat and work. Heat is not a state variable or state function; it is a process quantity. A thermodynamic system does not contain heat.