Definition of

Why is "variable" possibly having only one value? If x + 2 = 6, you can solve for x =, but in y = x + 2 (linear equation), x can take many values. Normally, it is always easier to call a variable even if it is a single value in some cases.

Entropy has two related definitions, thermodynamic definition and statistical mechanics definition. Historically, the classical thermodynamic definition was first developed. In a classical thermodynamic view, the system consists of a large number of components (atoms, molecules), whose state is described by the average thermodynamic properties of these components and the details of the system components are not taken into account directly, Their behavior depends on macroscopic average characteristics. For example, describe temperature, pressure, entropy, heat capacity and so on. The initial classical definition of the nature of the system is assumed to be in equilibrium. The classical thermodynamic definition of entropy has recently expanded to the field of non-equilibrium thermodynamics. The Newtonian particles constitute a gas and later form quantum mechanics (photon, phonon, rotation, etc.).

In the Boltzmann definition, entropy is a measure of the number of possible microscopic states (or microscopic states) of a system in thermodynamic equilibrium. In agreement with the definition of Boltzmann, it is necessary to paraphrase the second law of thermodynamics so that the entropy increases with time, but the basic remains the same. In thermodynamic systems, entropy is often roughly related to orderly, unorthodox, or chaotic things. The traditional qualitative description of entropy is a change in the present state of the system and is an index for measuring 'disorder of molecules' and is a measure of the amount of waste of energy that changes from one state or another state to dynamic energy is. In this direction, recent authors have derived accurate entropy expressions to explain and measure disorder and order in atoms and molecular aggregation.

The statistical definition was developed by analyzing the statistical behavior of the microscopic elements of the system by Ludwig Boltzmann in the 1970 's. Boltzmann shows that the definition of this entropy is equivalent to the thermodynamic entropy within the constant, which is later called the Boltzmann constant. In summary, the thermodynamic definition of entropy provides an experimental definition of entropy, the statistical definition of entropy extends the concept and provides an explanation and a better understanding of its nature.