In game theory, a solution concept is a formal rule for predicting how a game will be played. These predictions are called solutions, and describe which strategies will be adopted by players and, therefore, the result of the game. The most commonly used solution concepts are Economic equilibrium|equilibrium concepts, most famously Nash equilibrium.
Many solution concepts, for many games, will result in more than one solution. This puts any one of the solutions in doubt, so a game theorist may apply a refinement to narrow down the solutions. Each successive solution concept presented in the following improves on its predecessor by eliminating implausible equilibria in richer games.