Dramatic irony is created when an author permits the reader to understand more about a character's situation than the character understands at the time. In many instances of dramatic irony, the character acts in a way that is "grossly inappropriate" for the situation (Dr. Wheeler, "Literary Terms and Definitions: I"). One example of dramatic irony can be seen in Shakespeare's Romeo and Juliet. In act 1, scene 5, when Juliet first meets Romeo, she asks her nurse to find out what his name is and says that if she learns he is married, then her "grave is like to be [her] wedding bed." The irony here is that Shakespeare has foreshadowed enough, particularly in the prologue, that the reader already knows the fate of both Romeo and Juliet; hence, the reader knows Juliet's grave will indeed be her wedding bed, meaning that she will die either on or soon after her wedding day, even though Juliet does not yet know this herself.
In Gary Blackwood's The Shakespeare Stealer, we can see an example of dramatic irony in chapter 18. Here, Widge is trained by actors in the company on how to sword fight; however, they fail to tell him that the sword will collapse on impact just so that they can see the look of shock on his face when it happens. Hence, in this scene, the reader is told far more about what will happen with the sword than Widget is told.