Heat can also be defined as the amount of thermal energy in a system. Thermal energy is the type of energy that a thing has because of its temperature. In thermodynamics, thermal energy is the internal energy present in a system in a state of thermodynamic equilibrium because of its temperature. That is, heat is defined as a spontaneous "flow of energy" (energy in transit) from one object to another, caused by a difference in temperature between two objects; therefore, objects do not possess heat.