A tragedy was a type of literature genre where an honorable character suffered, either due to his own fault or due to external forces. A writer of tragedies was known as a tragedian.
William Shakespeare wrote many tragedies, such as Julius Caesar, King Lear, Macbeth, Othello, and Romeo and Juliet.
Elim Garak thought the fact that he realized Brutus would go on to kill Julius Caesar already 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")