Definitions for "Tetralogy"
A group or series of four dramatic pieces, three tragedies and one satyric, or comic, piece (or sometimes four tragedies), represented consequently on the Attic stage at the Dionysiac festival.
Four plays performed together in sequence. In ancient Greek theatre, this was the basic pattern for the tragic playwrights, who presented a trilogy of tragedies, followed by a satyr play.
a series of four related works (plays or operas or novels)