Effect may refer to: A result or change of something List of effects Cause and effect, an idiom describing causality Pharmacy and pharmacology Drug effect, a change resulting from the administration of a drug Therapeutic effect, a beneficial change in medical condition, often caused by a drug Adverse effect or side effect, an unwanted change in medical condition caused by a drug In media Special effect, an artificial illusion Sound effect, an artificially created or enhanced sound Visual effects, artificially created or enhanced images Audio signal processing Effects unit, a device used to manipulate electronic sound Effects pedal, a small device attached to an instrument to modify its sound Other uses Effects, one's personal property or belongings Effects (G.I. Joe), a fictional character in the G.I. Joe universe Effects (film), a 2005 film Effect size, a measure of the strength of a relationship between two variables Effect system, formal system which describes the computational effects of computer programs Pro-Design Effect, an Austrian paraglider design See also Affect (disambiguation) Effectiveness Efficacy Pragmatism, the philosophy of causes and effects