Canon

Canon is a term derived from Biblical scriptures, refering to the authoritative scriptures that cannot be removed or changed, and in fiction terms refers to the material that 'counts'. This use for fiction was originally devised by Sherlock Holmes fans, to distinguish the original Conan-Doyle stories from those by other writers: the original stories are the scripture and anything else written is derivative.

A second meaning for canon came along in later years: when the creator or rights holder declares that part of the official fiction counts and another part does not, and which is subject to change on the rights holder's whim. For example, CBS Entertainment count only the Star Trek TV shows as canon; when The Next Generation came out, The Animated Series was effectively 'decanonised' by Gene Roddenberry's office but in 2007, CBS declared it canon again.

We should note that when Holmes fan Ronald Knox used the term "canon" to describe Conan-Doyle's work, he was satirising his fellow fans and their obsession with what 'counted' in Conan-Doyle's 'lore' by comparing them to theologians.