In fiction, canon is the material accepted as officially part of the story in the fictional universe of that story.
It is often contrasted with, or used as the basis for, works of fan fiction.
The alternative terms mythology, timeline, universe and continuity are often used, with the first of these being used especially to refer to a richly detailed fictional canon requiring a large degree of suspension of disbelief (e.g. an entire imaginary world and history), while the latter two typically refer to a single arc where all events are directly connected chronologically.
Other times, the word can mean “to be acknowledged by the creator(s)”.
The use of the word canon originated in reference to a set of texts derived from Biblical canon, the set of books regarded as scripture, as contrasted with non-canonical Apocrypha.
The term was first used by analogy in the context of fiction to refer to the Sherlock Holmes stories and novels, written by Sir Arthur Conan Doyle, as contrasted with numerous Holmes adventures added later by other writers.
This usage was afterwards extended to the writings of various other authors.
Canonical or Non-Canonical
When there are multiple ‘official’ works or original media, the question of what is canonical can be unclear.
This is resolved either by explicitly excluding certain media from the status of canon (as in the case of Star Trek and Star Wars), by assigning different levels of canonicity to different media (as was in the case of Star Wars before the franchise was purchased by Disney), by considering different but licensed media treatments official and equally canonical to the series timeline within their own continuities universe, but not across them, or not resolved at all.
The use of canon is of particular importance with regard to reboots or re-imaginings of established franchises, such as the Star Trek remake (2009), because of the ways in which it influences the viewer experience.
The official Star Trek website describes Star Trek canon as “the events that take place within the episodes and movies” referring to the live-action television series and films, with Star Trek: The Animated Series having long existed in a nebulous gray area of canonicity. Events, characters and storylines from tie-in novels, comic books, and video games are explicitly excluded from the Star Trek canon, but the site notes that elements from these sources have been subsequently introduced into the television series, and says that “canon is not something set in stone.” Some non-canonical elements that later became canonical in the Star Trek universe are Uhura’s first name Nyota, introduced in the novels and made canonical in the 2009 film Star Trek, and James T. Kirk’s middle name Tiberius, introduced in the Star Trek animated series and made canonical in Star Trek VI: The Undiscovered Country.
The Star Wars canon originally existed on several levels. The highest level was the original Star Wars films, and statements by George Lucas; tie-in fiction from the Star Wars expanded universe had a different level of canonicity. The complex system was maintained by Leland Chee, a Lucasfilm employee. After Disney bought the franchise, all material published prior to 25 April 2014 that was not any of the Star Wars movies or the CGI cartoon The Clone Wars was declared in the ‘Legends’ continuity, marking them as no longer official canon. All subsequent material exists on the same level of canon, with the Lucasfilm Story Group being established to ensure no contradictions among canon works.
The makers of Doctor Who have generally avoided making pronouncements about canonicity, with Russell T Davies explaining that he does not think about the concept for the Doctor Who television series or its spin-offs.
Original Works vs Later Additions
In literature, the term canon is used to distinguish between the original works of a writer who created certain characters and/or settings, and the later works of other writers who took up the same characters or setting.
For example, the canon of Sherlock Holmes consists of the 56 short stories and four novels written by Sir Arthur Conan Doyle and featuring the detective Sherlock Holmes.
The subsequent works by other authors who took up Sherlock Holmes are considered non-canonical.
Influential or widely accepted fan theories may be referred to as ‘fanon’, a portmanteau of fan and canon. Alternatively, the term ‘headcanon’ is used to describe a fan’s own interpretation of a fictional universe.
Fan fiction is almost never regarded as canonical. However, certain ideas may become influential or widely accepted within fan communities.