system

A system is the set of rules and mechanics used to resolve actions in a role-playing game. It provides the procedures that determine what happens when a character attempts something with an uncertain outcome — how to decide whether an attack hits, whether a negotiation succeeds, or whether a character notices a hidden clue.

Systems vary along several dimensions. The resolution mechanism may use dice, cards, resource pools, or purely narrative authority. The level of detail ranges from rules-light systems that resolve most actions with a single roll and a conversation (Fate, Lasers & Feelings) to rules-heavy systems with detailed subsystems for combat, magic, crafting, social interaction, and more (GURPS, Pathfinder). The degree of player-facing mechanics varies: some systems give the game master broad adjudication power, while others distribute narrative authority among all players.

A system shapes play by determining which actions the game treats as interesting enough to model with rules. A system with detailed combat mechanics and no social mechanics implicitly tells the group that fighting is the game’s focus. A system with extensive downtime rules assumes that what characters do between adventures matters. The choice of system is often the most consequential decision a group makes during session zero, because it determines not just how the game is played but what kinds of stories it is designed to produce. A system is distinct from a setting, though the two are frequently published together and can be difficult to separate in practice.