Please give an example of dramatic irony from Act 5 in Macbeth? Offer a description of why and how is it dramatic irony.

Much dramatic irony abounds in Act 5 of The Tragedy of Macbeth.  One example is in Scene 1.  The doctor and gentlewoman overhear Lady Macbeth sleepwalking and talking about the blood on her hands.  Lady Macbeth continues to mutter, "Out, damned spot!" but the doctor and gentlewoman do not know what she means.  They think that she has gone mad, but the reader knows that this act is a manifestation of the guilt that Lady Macbeth feels over pushing Macbeth into the murder of Duncan.  Macbeth has also killed all of Macduff's family, and Lady Macbeth feels sympathy for Lady Macduff who was innocent in this situation.  Dramatic irony refers to events that are known by the reader and some characters which are unknown to other characters.  So here the doctor and gentlewoman are unaware of Lady Macbeth's (and Macbeth's) role in the murders while the reader has known all along their greedy intentions.