In all of the examples from the last section, whatever one player won, the other player lost. A two-player game is called a zero-sum game if the sum of the payoffs to each player is constant for all p...In all of the examples from the last section, whatever one player won, the other player lost. A two-player game is called a zero-sum game if the sum of the payoffs to each player is constant for all possible outcomes of the game. More specifically, the terms (or coordinates) in each payoff vector must add up to the same value for each payoff vector. Such games are sometimes called constant-sum games instead.