English headcanonIdeas about a fictional work that individual fans have come up with and accept as true for themselves without the official authors necessarily supporting (or denying) them.

Canon delimits the notions and ideas that have officially been sanctioned by the creative powers behind a work. For example a author of a spy novel might confirm that a particular character in her books is secretly working for a foreign government. Headcanon by contrast marks ideas that individual fans have come up with themselves but that aren't necessarily supported by the author. This happens for example when for the same book a reader conjures up and accepts the idea that a particular character's erratic actions are caused by the early onset of a disease without the novel or supporting material giving any concrect indications for this (but the idea still being sensible) than they have just established their own headcanon. [https://www.merriam-webster.com/words-at-play/words-were-watching-headcanon-fanon](https://www.merriam-webster.com/words-at-play/words-were-watching-headcanon-fanon)