What is tragedy? I am looking for a literary definition and source.
Tragedy is a genre of play in which the main character experiences a demise due to a flaw in their character.
I am assuming with this answer that you mean the genre of tragedy and not any other definition.
Some examples of this include Macbeth who experiences both a downfall of power and death due to his tragic flaw which is ambition.
I'm afraid my source is my year 8 English teacher, but I suppose you could use the Collins English Dictionary.