Hamartia is a Greek word that means "tragic flaw" or "error in judgment." In the context of Greek tragedy, hamartia is the mistake or weakness that leads to the downfall of the protagonist. In Oedipus' case, his hamartia is his arrogance and pride. He believes that he is so wise and powerful that he can escape the fate that has been predicted for him. This leads him to make a series of rash decisions that ultimately lead to his downfall.