Nash equilibrium is a fundamental concept in the theory
of games and the most widely used method of predicting
the outcome of a strategic interaction in the social sciences.
A game (in strategic or normal form) consists of the
following three elements: a set of players, a set of actions
(or pure-strategies) available to each player, and a payoff
(or utility) function for each player. The payoff functions
represent each player’s preferences over action profiles,
where an action profile is simply a list of actions, one for
each player. A pure-strategy Nash equilibrium is an action
profile with the property that no single player can obtain
a higher payoff by deviating unilaterally from this profile.