Equilibrium

Equilibrium or balance is any of a number of related phenomena in the natural and social sciences. In general, a system is said to be in a state of equilibrium if all influences on the system are cancelled by the effects of others. A related concept is stability; an equilibrium may or may not be stable.

Some specific examples are:

Chemical equilibrium, the state in which a chemical reaction proceeds at the same rate as its reverse reaction, resulting in no net change in the amount of each compound.

Mechanical equilibrium, also known as static equilibrium, the state of a body at rest or in uniform motion in which the sum of all forces and torques acting on the body equals zero.

Physical balance of humans and animals is maintained with the aid of the sense of balance, and in special cases with a balance beam.
See also the weighing instrument balance.

Thermodynamic equilibrium, the state of a system in which its internal processes cause no net change in its macroscopic properties (such as temperature and pressure).

In economics, static equilibrium and general equilibrium

Nash equilibrium in game theory, an optimum strategy for all players in a game, in the sense that no one player can benefit by changing his strategy while all other players keep theirs the same.

Reflective equilibrium in ethics, a state in which the consequences of one's general principles are consistent with one's opinions about individual cases.

For individuals and organisations a balance between income and expenses is often important, especially in the long run.

Psychologically some balance between desires and satisfaction is important; somewhat paradoxically complete satisfaction may not be ideal, it can be argued that perhaps it is better if things are left to be desired.

In various practical matters an equilibrium is useful, e.g.:

in a conversation, between talking and listening;
in a personal relationship, between giving and taking;
between buying and reading books (apart from lent books).

An addiction is any of various forms of unbalanced behavior.

Equilibrium

Further reading