Retroactive continuity, or retcon for short, is a literary device in which facts in the world of a fictional work that have been established through the narrative itself are adjusted, ignored, supplemented, or contradicted by a subsequently published work that recontextualizes or breaks continuity with the former.
The Death of Sherlock Holmes: Sir Arthur Conan Doyle employed retroactive continuity to explain Sherlock Holmes's return after his death in an earlier story fighting his enemy, Professor Moriarty.
In fiction, continuity is the consistency of the characteristics of people, plot, objects, and places seen by the audience over some period of time. It is relevant to many genres and forms of storytelling, especially if it is long-running.
A continuity error in Charlie Chaplin's 1914 comedy short The Property Man. In the first frame, Chaplin's character is seen carrying a trunk through a door, holding his hat behind him. In the immediately subsequent shot from the other side of the door, he is wearing the hat.