As nouns the difference between irony and fallacy
is that
irony is a statement that, when taken in context, may actually mean something different from, or the opposite of, what is written literally; the use of words expressing something other than their literal intention, often in a humorous context while
fallacy is deceptive or false appearance; deceitfulness; that which misleads the eye or the mind; deception.
As an adjective irony
is of or pertaining to the metal iron.