Retcon
A retcon (retroactive continuity) is a new story that changes what had previously happened in a series' past, rewriting earlier events or revealing they were not what they seemed.
Where the word comes from
Short for retroactive continuity; the phrase was in use among comics readers and writers by the 1980s.
In depth
Retcons alter the established past: a character who died turns out to have survived, a hero's origin acquires a hidden detail, or an entire storyline is declared never to have happened. They range from small clarifications to wholesale rewrites, and are often introduced to reconcile contradictions or to let a writer take a character in a new direction.
In practice
Retcons are most common in long-running shared universes, where decades of stories by different writers inevitably contradict each other. Crossover events and reboots frequently carry large retcons with them.
Kinds of retcon
Some retcons add information without contradicting anything — a newly revealed childhood friend, a secret kept until now. Others change established events, such as reversing a death or rewriting an origin. The largest are linked to reboots and events that rearrange an entire universe's history at once.
Reading around them
For readers of collected editions, retcons mostly matter when moving between eras of a character. A good reading order notes where a later story changed an earlier one, so the older book can still be enjoyed as it was written.
What it means today
If an older story seems to contradict a newer one, a retcon is usually why; reading orders note where they happened.
