In the play written by Sophocles, Oedipus the King, there are several instances of irony. Dramatic irony, or tragic irony as some critics would prefer to call it, usually means a situation in which the character of the play has limited knowledge and says or does something in which they have no idea of the significance. The audience, however, already has the knowledge of what is going to occur or what the consequences of the characters actions will be. The degree of irony and the effect it has depends upon the readers' grasp and recognition of some discrepancy between two things.
This is an example of situational irony, in which the wife sells her most prized possession – her hair – to get her husband a Christmas present; and the husband sells his most dear possession – the gold watch – to get his wife a Christmas present. By the end, it is revealed that neither has the utility of the present bought by the other, as both sell their best things to give the other one a gift. Combs, the gift for the wife, is useless because she has sold her hair. The gold watch chain, the gift for the husband, is useless because he has sold the watch to get the combs. The situation becomes ironic for such an incident.