Ancient Greek Tragedy in the 5th century BCE for the stage consisted of the chorus of probably around 12 members  and the actor(s). Early drama probably only had one actor and Aeschylus added a second actor. Sophocles is credited with adding a third actor. No other actors were ever added and all the actors were men, even for the roles of women. Only two or three characters were present on stage at any one time with actors leaving the stage and returning as a different character wearing a different mask. Our manuscripts of these plays have NO STAGE DIRECTIONS AT ALL. They do not even tell us who is speaking which parts. All our current knowledge is based on scholars who have managed to deduce which characters would be on stage at any particular time to speak each written dialogue for a particular play.

(The Great Courses – Greek Tragedy)