Explain three unities related to Oedipus Rex.

Aristotle's three unities are unity of place, unity of time, and unity of subject.  Oedipus Rex, Sophocles's tragedy, achieves all three of the Aristotelian unities.  

First, it achieves unity of place because all of the action happens only in one place: in front of Oedipus and Jocasta's royal residence.  Whenever the characters need information, they call someone to them rather than leaving this place; or, when events occur inside, someone comes out...

Aristotle's three unities are unity of place, unity of time, and unity of subject.  Oedipus Rex, Sophocles's tragedy, achieves all three of the Aristotelian unities.  

First, it achieves unity of place because all of the action happens only in one place: in front of Oedipus and Jocasta's royal residence.  Whenever the characters need information, they call someone to them rather than leaving this place; or, when events occur inside, someone comes out to tell the characters.

Second, the play adheres to the unity of time because everything takes place within twenty four hours.  For example, instead of having Oedipus decide to send Creon to the oracle during the course of the play, and then having to wait several days for him to return with his news, Sophocles has Oedipus think ahead and send Creon several days before anyone suggests it; that way, Creon can return at just the right time to deliver his information so that the play can promptly continue.

Third, the play achieves unity of subject by only focusing on Oedipus's tragedy.  There are no subplots or story lines that focus on other characters to distract us from Oedipus's immense pride and tragic end.