Aristotle's Definition of Tragedy

  imitation button action serious complete magnitude language embellished parts of the ply persons performing pity ad fear purification tragic acts  

Philoctetes

χωρὶς ἑκάστῳ τῶν εἰδῶν ἐν τοῖς μορίοις /
several kinds being found in the parts of the play

Again, making the comparison with epic poetry, Aristotle observes that tragedies not only employ a variety of verse forms, but that the forms vary from one part of the drama to another; with particular variation between the dialogue to the choral odes.