There are three ancient terms having to do with the theater still used today, but with a different meaning.
The orchestra is a round or semi-circular paved area where the chorus sings and dances. The word itself means ‘place for dancing’. The shape of the orchestra may have been determined by the round threshing floor used for threshing grain, which at festival time was used as a dancing floor in the Greek countryside. As mentioned earlier, in the center of the orchestra was a sacrificial altar.
Theatron ('a viewing area') is that part of the ancient theater from which the audience views the drama and is not used of the whole structure.
Skene (‘tent’, ‘stage building’) is a wooden construction with a flat roof in front of which actors acted out their roles. The skene usually represented a palace (sometimes a temple), although the occasional play that required a natural setting could be accommodated with a set representing rocks. The skene was also used as a dressing room and storage area for props. The actors performed on a shallow apron in front of the skene which was connected with the orchestra by stairs only a few feet high. These stairs allowed the actors to join the chorus in the orchestra when necessary.
Parodos is a gangway leading into the orchestra over which chorus and actors made their entrances. There are two parodoi, one on each side of the orchestra. Parodos is also the name of the song chanted by the chorus as they entered the orchestra at the beginning of the play.
The seating arrangement of the Theater of Dionysus is an aesthetically pleasing arrangement of tiers of seats consisting of concentric arcs rising up the slope of a hill. Radial staircases separate the viewing into wedge-shaped sections (kerkides). The radial staircases were necessary for the quick entrance and exit of a large crowd. It has been estimated that the Theater of Dionysus in the late fourth century could hold up to 17,000 spectators.