Definition of entropy


Entropy is a fundamental concept in thermodynamics representing the degree of disorder or randomness in a system.

It's a state function that quantifies the number of specific ways in which a system may be arranged, often taken to be a measure of "molecular disorder".

The second law of thermodynamics states that in any isolated system, entropy will always increase or remain constant over time, implying that natural processes prefer states of higher entropy.

Category/Context: Thermodynamics, Physical Chemistry, Statistical Mechanics

Related Terminology

Second Law of Thermodynamics, Gibbs Free Energy, Enthalpy, Boltzmann's Entropy Formula, Microstate, Macrostate


Entropy is critical in understanding spontaneous processes, chemical reactions, heat transfer, and the fundamental direction of time. In chemistry, it helps predict the feasibility of reactions.

Student Level: This definition is suitable for high school and undergraduate chemistry students.

Etymology/History: The term "entropy" was introduced by Rudolf Clausius in the 19th century, deriving from the Greek word "entropia," which means "a turning toward" or "transformation."

source: Entropy | physics. (n.d.). Encyclopedia Britannica Link Entropy. (n.d.). Chemistry LibreTexts Link