A dissipative system (or dissipative structure) is an open system which is operating far from thermodynamic equilibrium within an environment that exchanges energy, matter or entropy. A dissipative system is characterized by the spontaneous appearance of a complex, sometimes chaotic, structure. The term dissipative structures was coined by Ilya Prigogine.

A simple example is the Bénard cells. More complex examples include lasers, Belousov-Zhabotinsky reaction, or even life itself.

Quantum dissipative systems

As quantum mechanics relies heavily on Hamiltonian mechanics, it is not intrinsically able to describe dissipative systems. In principle one can couple weakly the system, say an oscillator, to a bath, i.e., an assembly of many oscillators in thermal equilibrium with a broad band spectrum, and trace (average) over the bath. This yield a master equation which is a special case of a more general setting called the Lindblad equation.

See also: self-organization - autopoiesis - dynamical systems and chaos theory

Another meaning of "dissipative system" is one that dissipates heat, see heat dissipation.