A tragedy is a type of literature where an honorable character suffers their downfall, sometimes a fault of their own and others due to external forces. William Shakespeare wrote many tragedies, such as Julius Caesar, King Lear, Macbeth, Othello and Romeo and Juliet.
Elim Garak thought that the fact that he saw that Brutus would kill Julius Caesar in the first act meant that Julius Caesar was more a farcical play than a tragedy. Julian Bashir disagreed, as he felt that the fact that Caesar did not suspect his best friend of plotting his murder was the tragedy. (DS9: "Improbable Cause")