Defining Games: Caillois’ terminology

James Newman uses Roger Caillois’ idea of Paidia and ludus.

Paidia means Play for pleasure.

Ludus means being constrained by rules, with a clear outcome. 

To simply these meanings Paidia is the ability to play the game freely in whatever way you want for the purpose of enjoying yourself. While Ludus is playing a game while constrained by tight rules for the purpose of winning. 

Newman also talks about aspects of gameplay. These aspects are Agon, Alea, Ilinx and Mimicry.

Agon means competition. Alea means Chance or randomness. Ilinx means movement and Mimicry means Simulation or role play.