The so-called entropy in chemistry and thermodynamics is a measure of the total amount of energy that cannot be done in terms of kinetics. That is, when the entropy of the population increases, its functional power also decreases. The measure of entropy is an indicator of energy degradation. Entropy is also used to calculate the out-of-order phenomenon in a system, that is, to calculate the degree of confusion in the system. Entropy is a function that describes the state of the system, but it is often analyzed and compared with the reference value and variation of entropy. It has important applications in cybernetics, probability theory, number theory, astrophysics, life sciences, etc., in different disciplines. There are also more specific definitions that are derived and are important parameters in various fields.

The reason for the entropy can be understood as the energy conversion, most of the energy will be converted into a preset state, such as thermal energy into mechanical energy, electrical energy into light energy. However, there is still a part of the energy that will generate a new state, which can be seen as entropy.