A broadly used term with multiple meanings. It often is used to mean all concrete mechanics within a published game, including character creation, conflict or task resolution, experience, and any other text phrased as a rule to the players. On the Forge, "System" is sometimes defined more broadly as "the means by which imaginary events are established during play" (see the Lumpley Principle).

In practice, published role-playing game rules cover different scope. As a simple example, some games specify a setting; while other games leave that up to the group. Going further, Puppetland (by John Tynes) has a rule that anything a player says while sitting down is in-character. Most games never depend on whether a player is sitting, and have no rules that define when a player is speaking in character. The example simply illustrates that written rules can potentially define any part of the game. In addition, the written rules may specify who the characters are, as some LARPs do.

Depending on their view, people may have different understandings of what subset of the game as a whole constitutes "System".

References:

• rec.games.frp.advocacy FAQ Part I (December 1998)
• Vincent's standard rant: power, credibility, and assent (The Forge, Oct 2002)
• The Provisional Glossary by Ron Edwards (Mar 2004)