Aristotle's Tragedy Terminology

In movies, or on television or stage, actors interact with one another and speak lines from their scripts. If there's only one actor, it's a monologue. Ancient tragedy began as a conversation between a single actor and a chorus performing in front of an audience. A second and, later, a third actor were added to enhance tragedy, which was a major part of Athens' religious festivals in honor of Dionysus. Since dialogue between individual actors was a secondary feature of Greek drama, there must have been other important features of tragedy. Aristotle points them out.