## Quick Reference

In game theory, a profile of strategy (2) choices such that every player's strategy is a best reply to the strategies chosen by the other players. Given the strategies chosen by the other players (or, if there is only one, the strategy chosen by the other player), a best reply is a strategy that gives the player choosing it at least as good a payoff as any other strategy. A key property of a Nash equilibrium is that no player has any incentive to deviate unilaterally from it, so that it gives the players no cause to regret their strategy choices when the other players' choices are revealed. It is a basic tenet of game theory that a rational solution to any game must be a Nash equilibrium, but many games have multiple Nash equilibria. Also called an *equilibrium point* or an *equilibrium*. See also minimax theorem. [Named after the US mathematician John F(orbes) Nash (born 1928) who introduced it in articles in the Proceedings of the National Academy of Sciences in 1950 and the Annals of Mathematics in 1951]

*Subjects:*
Social Sciences — Psychology.

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