Umpire
[JV43] An arbitrator for a game who has a non-player role, but who can supply information to the players concerning the state of play, e.g., signaling illegal moves when a player must make a move without full knowledge of its feasibility. In particular, within game theory, the umpire provides the player choices that are left to chance.

Utility
[JV43] Utility is a fundamental concept employed in Game Theory. Utility is a means of defining individual preferences, especially as relates to choices made in a game context. Utility has certain fundamental mathematical assumptions associated with it that allow for the comparison of utility between situations and when associated with “payoff”. The set of utilities corresponding to a set of choices (at any given instant) can be rank ordered by the users preferences.