The term hamartia derives from the Greek verb hamartánein, which means to miss a mark (as when an arrow does not hit an intended target) or to stray from a path (as when one gets lost in the woods). The particular sense of hamartia relevant to tragic plot is that once an improperly aimed arrow has been released from a bow, it cannot be taken back. Rather than being a moral failing, the Greek term is actually neutral, emphasizing a mistake that cannot be undone and thus culminates in a disaster. Thus in a tragic plot, according to Aristotle, the audience feels fear and pity at the spectacle of a noble character headed on a course that will inevitably lead to that person's destruction.
For Aristotle, the trajectory of a tragic plot must be one of downfall, in which a great and noble person is brought to great misery or suffering. At the point in the plot where one encounters hamartia, the character's downfall becomes unavoidable because a certain decision, such as Oedipus's quest for the truth or Creon's condemnation of Antigone, cannot be reversed or taken back. At times, the root of hamartia may be a curse on a family or a situation in which all possible actions lead to disastrous consequences.
For Aristotle, without this narrative trajectory, a work cannot be considered a tragedy. In comedy, for example, Aristotle would argue that the characters can be despicable and make mistakes, but those mistakes are ones that evoke laughter rather than pity, and often the consequences of the characters' actions are not inevitable downfall. Epic also does not require the presence of a specific plot involving hamartia. Thus, for Aristotle, the notion of hamartia is a defining characteristic of a specific genre of drama rather than a requirement for all forms of verse and drama.