Pareto efficiency is a state of resource allocation where it is impossible to make one individual better off without making at least one other individual worse off.

The Kaldor-Hicks criterion states that a policy is beneficial if it makes at least one individual better off without making anyone worse off, even if the policy makes some individuals worse off.

A Nash equilibrium is a set of strategies where no player can improve their outcome by changing their strategy while the other players keep their strategies unchanged.

The prisoner's dilemma is a game theory model that shows how rational self-interest can lead to suboptimal outcomes for all players, even when cooperation would be mutually beneficial.

In a zero-sum game, the gains of one player are exactly offset by the losses of the other players, so the total payoff to all players is zero.

The Cournot model of oligopoly is a game theory model that assumes that firms compete in quantity, taking the output of other firms as given.

The Bertrand model of oligopoly is a game theory model that assumes that firms compete in price, taking the prices of other firms as given.

In a monopolistic competition market, firms produce differentiated products, have market power, and face downward-sloping demand curves.

The Hotelling model of spatial competition is a game theory model that assumes that firms are located along a linear market, compete in prices, and consumers are uniformly distributed along the market.

The Coase theorem states that in the absence of externalities, the allocation of resources will be efficient regardless of the initial allocation of property rights.

The Pigouvian tax is a tax that is imposed on negative externalities in order to internalize the cost of the externality and achieve an efficient allocation of resources.

The Bator model of optimal taxation is a model that determines the optimal level of government spending, the optimal tax rates on different goods and services, and the optimal distribution of income.

The Mirrlees model of optimal income taxation is a model that determines the optimal tax rates on different levels of income.

The Atkinson-Stiglitz model of optimal taxation is a model that determines the optimal distribution of income.

The Diamond-Mirrlees model of optimal taxation is a model that determines the optimal level of government spending, the optimal tax rates on different goods and services, and the optimal distribution of income.