ABSTRACT"Player modeling" is a loose concept. It can equally apply to everything from a predictive model of player actions resulting from machine learning to a designer's description of a player's expected reactions in response to some piece of game content. This lack of a precise terminology prevents practitioners from quickly finding introductions to applicable modeling methods or determining viable alternatives to their own techniques. We introduce a vocabulary that distinguishes between the major existing player modeling applications and techniques. Four facets together define the kind for a model: the scope of application, the purpose of use, the domain of modeled details, and the source of a model's derivation or motivation. This vocabulary allows the identification of relevant player modeling methods for particular problems and clarifies the roles that a player model can take.