statistical mechanics

American  

noun

Physics, Chemistry.

1. the science that deals with average properties of the molecules, atoms, or elementary particles in random motion in a system of many such particles and relates these properties to the thermodynamic and other macroscopic properties of the system.

---

statistical mechanics British  

noun

1. (functioning as singular) the study of the properties of physical systems as predicted by the statistical behaviour of their constituent particles

---

statistical mechanics Scientific  

/ stə-tĭs′tĭ-kəl /

1. The branch of physics that applies statistical principles to the mechanical behavior of large numbers of small particles (such as molecules, atoms, or subatomic particles) in order to explain the overall properties of the matter composed of such particles. The kinetic theory of heat is an example of statistical mechanics; the laws of thermodynamics can all be explained using statistical mechanics. Both classical physics and quantum mechanics have been used in the development of statistical mechanical theories.

2. ◆ Bose-Einstein statistics explains the behavior of large numbers of bosons, which are particles that can simultaneously occupy the same quantum state (such as photons in a laser beam).

3. ◆ Fermi-Dirac statistics explains the behavior of large numbers of particles that obey the Pauli exclusion principle (such as electrons) and cannot simultaneously occupy the same quantum state.

---

Etymology

Origin of statistical mechanics

First recorded in 1880–85

Example Sentences

Throughout a prolific career, he worked across all areas of physics, but maintained particular interest in the fields of statistical mechanics and symmetry principles.

From BBC • Oct. 18, 2025

Second, they used statistical mechanics to mathematically predict the behavior of the puffs, using techniques from phase transition physics.

From Science Daily • Jun. 3, 2024

Conformal field theory acts as a bridge between different fields of physics: the underlying math is used in string theory, condensed matter physics and quantum statistical mechanics.

From Scientific American • Sep. 25, 2023

Dr. Anderson once called spin glasses a “bridge between biology, statistical mechanics, and computer science.”

From New York Times • Mar. 30, 2020

From thermodynamics came the discipline of statistical mechanics.

From "Zero: The Biography of a Dangerous Idea" by Charles Seife