Greek tragedy originated from the dithyramb, a hymn to Dionysus. There are various hypotheses about the origins of the term "tragedy" including that it comes from the Greek words for goat and song. Aristotle defined key concepts of tragedy including imitation, catharsis, hamartia, and the tragic hero. Tragedies were performed as part of religious festivals, usually featuring three playwrights each presenting three tragedies and a satyr play over three days.