To understand dramatic irony, it is important to understand the meaning of irony and the three basic types of irony.
Irony basically means “To say one thing but to mean something else.”
Irony defined is a dryly humorous figure of speech in which the literal meaning of a word or statement is the opposite of that intended. In literature, it is the technique of indicating an intention or attitude opposed to what is actually stated.
Many stories will have one or more of these types of irony: verbal; situation; and/or dramatic.
Verbal irony---This type of irony has comes when words have a duality of meaning. This is the classic form of irony. The words that are used carry a double message. The first meaning of the word runs parallel to the mocking or sardonic meaning ascribed to the word. Irony is neither bitter nor sarcastic. The character in the story primarily uses his ironic words as controlled exaggeration.
Situational irony—This type of irony is found when actions have an effect that is the opposite from what was intended or expected. Situational irony is also called irony of events. This irony is best defined as a situation where the outcome is inconsistent with what was anticipated. An example might be if a man takes great care to avoid stepping in dog poop and instead slips and falls in it because of a banana peel.
Dramatic irony—This type of irony is used when the audience has knowledge of the fate awaiting the characters. "The characters expect their actions to lead them to triumph, but since readers know what lies in store, the characters’ confidence is ironic." Dramatic irony makes the characters have an inescapable fate, which replaces suspense with tension as readers know that outcome.
In addition, dramatic irony occurs when "the words and actions of the characters have a different meaning for the audience or reader than they have for the characters." The reader knows more than the characters do.
Examples of dramatic irony
“The Cask of Amontillado” is a perfect example of dramatic irony. Montresor, a murderer, relates the details of the murder of his enemy fifty years after the crime. Fortunato, his rival, insults Montresor. The reader knows from the beginning what is in store for the ironically named Fortunato, who fate is not lucky. Montresor lures Fortunato down into a catacomb by referring to Fortunato’s weakness, wine. Montresor claims that he knows that Fortunato is an expert concerning Amontillado, a rare wine. Fortunato expects to drink some wine. Because he has already had too much to drink, he misses very clue that Montresor drops along the way. The story culminates in the shackling of Fortunate in a niche and being entombed while alive.
Another example comes from Shakespeare’s Julius Caesar. In Act II, Julius Caesar’s wife Calpurnia has a bad dream which frightens her. She tells Caesar that he should not go to the Capitol despite the fact that he is to be offered the crown of Rome that day. After hearing from the prophets who have opened an animal and discovered it had not heart, Caesar decides that he will stay at home. The audience knows that the conspirators plan to assassinate him that day. When all of the conspirators show up to escort Caesar to the senate, Caesar is proud that his good friends have come to take him to the Capitol. He changes his mind and goes with them. The audience knows that he goes to his death. This is dramatic irony.