Irony is a literary or rhetorical device, in which there is an incongruity or discordance between what one says or does, and what one means or what is generally understood.

In modern usage, it can refer to incongruity between the intended meaning of an action and the actual or perceived meaning of an action.

There is some argument about what is ironic, but all the different senses of irony revolve around the perceived notion of an incongruity between what is said and what is meant; or between an understanding of reality, or an expectation of a reality, and what actually happens.

The term Socratic irony, which was coined by Aristotle, refers to the Socratic Method. It is not irony in the modern sense of the word.

Definitions

Henry Watson Fowler, in The King's English, says “any definition of irony—though hundreds might be given, and very few of them would be accepted—must include this, that the surface meaning and the underlying meaning of what is said are not the same.”

The word 'ironic' is sometimes used as a synonym for incongruous or coincidental in situations where there is no “double audience,” and no contradiction between the ostensible and true meaning of the words. An example of such usage:

Ironically, Sir Arthur Sullivan is remembered for the comic operas he found embarrassing, rather than the serious works he hoped would be his legacy.

The American Heritage Dictionary recognizes a secondary meaning for irony: “incongruity between what might be expected and what actually occurs.” This sense, however, is not synonymous with "incongruous" but merely a definition of dramatic or situational irony. The American Heritage Dictionary's usage panel found it unacceptable to use the word ironic to describe mere unfortunate coincidences or surprising disappointments that “suggest no particular lessons about human vanity or folly.”

Types of irony

These modern theories of rhetoric distinguish between three types of irony: verbal, dramatic and situational.

• Verbal irony is a disparity of expression and intention: when a speaker says one thing but means another, or when a literal meaning is contrary to its intended effect. An example of this is sarcasm.
• Dramatic (or tragic) irony is a disparity of expression and awareness: when words and actions possess a significance that the listener or audience understands, but the speaker or character does not.
• Situational irony is the disparity of intention and result: when the result of an action is contrary to the desired or expected effect. Likewise, cosmic irony is disparity between human desires and the harsh realities of the outside world (or the whims of the gods). By some older definitions, situational irony and cosmic irony are not irony at all.