The mechanismA gap with an audience
Something is out of joint — saying and meaning, expectation and outcome, knowledge and ignorance — and the text positions someone to see it. No second vantage point, no irony.
Original example — verbal
“Perfect weather for the roofers,” she said, into the hail.
The speaker means the opposite of her words, and the scene makes sure we hear both faces at once. Sarcasm is only irony’s loudest register.
Three flavors, three gapsVerbal · Situational · Dramatic
Verbal: the speaker’s words point one way, her meaning the other.
Situational: the outcome inverts an expectation the text itself built — the safety inspector’s report on the theater fire perishing in the theater fire is ironic only if the text first established the archive as the thing that survives.
Dramatic: the audience holds a fact a character cannot — we have read the letter; the daughter, saving it unopened for her birthday, keeps thanking the uncle who wrote it.
Cite it when you can name both sides of the gap and who occupies each. The gap measures distance; your essay says what the distance means.