Ironic Distance
The narrator can generally see into the minds of the main characters of this novel, telling us what is going on in their heads. However, at times he ironically restricts his point of view, claiming that he does not know what goes on in their minds, but that he is only imagining it. This technique of 'ironic distance', where the narrator claims there is a disparity between what he reports and what the character experiences, is often used to provide an approximate figuration of a character's subconscious thoughts.
Verbal Irony
'Verbal irony' is when someone says something and means something else. So for example, when Madame Merle declares that she feels like she is the clothes that she wears, that a person is nothing but his or her accouterments, the signs that he or she gives off, Merle is expressing herself ironically. She is pretending to be forthright and frank with Isabel, but the meaning of her words can only be that her words do not express any authentic idea at all.
Dramatic Irony
'Dramatic irony' occurs when a character acts on knowledge or articulates something that the reader knows to be untrue. So, for example, when Osmond tells Isabel that she ought to honor her marriage vow to him and not visit Ralph, he tells he forbids the visitation: "Because I think we should accept the consequences of our actions, and what I value most in life is the honour of a thing!" This is ironic because the reader knows that Osmond is not an honorable person. The very fact of his articulating this shows how he is willing to use Isabel's own sense of honor against her -- how dishonorable he is.
Situational Irony
When a narrative creates certain expectations due to the circumstances in a story, does not fulfill these expectations, and then shows a resulting situation that is perversely appropriate to the circumstances instead, this can be said to be ‘situationally ironic’. So for example, Isabel's promise of asserting her freedom and her own idea in life sets up the expectation that she will do something great and original, something unexpected. However, she ends up fulfilling these expectations ironically by marrying Osmond -- nobody expected her to marry Osmond, nor did anyone want her to, and this then has the appearance of being an "original" idea of her own. The perversity of this is that a marriage to Osmond disallows her from expressing herself as she is.
