Greek drama has made a significant contribution to the art of the Dramatic Play. There exist a plethora of dramas from Ancient Greek times. As noted above, costuming was important and the performers would engage in chanting their lines or narrating or reciting them.
Important to understand is that the uniqueness of Greek plays was that dramas were dramas and comedies were comedies and “never the twain shall meet”. In other words, dramas were not peppered with comedic lines and moments or scenes. Neither were comedies dealing in tragedy and serious drama. The Greeks kept a distinction between these two types of plays. Today, it is common to see dramas and comedies have elements of both in each other.
Now, Greek drama also had a well-defined beginning, middle, and end. The play progressed clearly and systematically to its conclusion. There was no playing around really with structure. Contemporary drams, for example, will play with structure and be more experimental, as will film.
Concerning film, French film director Jean-Luc Godard said, "A film should have a beginning, middle, and an end, but not necessarily in that order." This philosophy of dramatic presentation is also apparent in contemporary theatre in some cases and there is nothing wrong with that; it’s just a different way of approaching dramatic subjects.
The chorus was a mainstay of Greek drama. The chorus could reveal information to the audience that the characters did not know. It could also be information that the audience comes to know from the chorus, that the character or characters did not know that they knew. In the dramatic happenings, the characters, as written by the playwright, are somewhat oblivious to what they actually know and this adds to the drama of the play. Today, in modern playwriting, the chorus is an archaic theatre convention.
Furthermore, singing was often a vital part of Greek drama and many plays had a religious bent to them. Of course, today, we have singing in many types of plays (the preponderance of musicals, as well), but the amount of plays closely associated with religion are less so than in Ancient Greek times.