Activity may mean: action, in general physical activity Activity, an alternative name for the game charades Activity, a task. Activity, the ability of a piece to influence the game in chess Activity, the rate of a catalytic reaction, such as enzyme activity, in physical chemistry and enzymology activity (chemistry), the effective concentration of a solute for the purposes of mass action activity (project management) activity (radioactivity), the number of radioactive decays per second… (More on Activities)