https://en.wikipedia.org/wiki/Hedonic_game中介绍为:“In cooperative game theory, 
a hedonic game[1][2] (also known as a (hedonic) coalition formation game) is a game that models the formation of coalitions (groups) of players when players have preferences over which group they belong to. A hedonic game is specified by giving a finite set of players, and, for each player, a preference ranking over all coalitions (subsets) of players that the player belongs to. The outcome of a hedonic game consists of a partition of the players into disjoint coalitions, that is, each player is assigned a unique group. Such partitions are often referred to as coalition structures.”---其中红色的部分括号中“
hedonic”为什么被括起来?