Star Trek canon
The Star Trek canon consists of the television series Star Trek, Star Trek: The Next Generation, Star Trek: Deep Space Nine, Star Trek: Voyager, Star Trek: Enterprise, and the ten motion pictures based upon the franchise.
The non-canonical status of the various novels, comic books and Star Trek: The Animated Series was decided by Gene Roddenberry, who also said he considered elements of the Trek films Star Trek V: The Final Frontier and Star Trek VI: The Undiscovered Country to be apocryphal, although these films remain full canon.
According to current editors at Pocket Books, current rights holders for publishing Star Trek fiction, no novels or other printed stories are considered canon by Paramount Pictures, owners of Star Trek. This includes the Voyager novels Pathways and Mosaic (both by the series producer Jeri Taylor) which were, for a time, considered canon but stopped being so after Taylor left her position with the series. This viewpoint is considered controversial by many fans of Star Trek fiction, some of whom consider the literary works to be superior to many examples of the televised and filmed Star Trek.
In addition, no reference works based upon the series are considered canon, either, even though they may contain canonical elements. This includes works such as the popular Star Trek Chronology.
Various official computer games based on Star Trek have been released -- often by Paramount Pictures' sister firm Simon and Schuster -- but these, too, are discontinuous from the canon.
No animated series episode is considered canon; however, elements from the animated series have been introduced into canon by clever live-action episode writers, an example being the "Kaswahn" ritual mentioned in the episode "Yesteryear" which remained officially non-canonical until it was mentioned in a 2002 episode of Star Trek: Enterprise called "The Catwalk." Many Star Trek fans do not accept the Enterprise series as canon, with some alleging it violates continuity with earlier series and movies, and others basing their opinion on it violating aspects of fanon. Others believe it takes place in an alternate universe that follows a different timeline than that established in the Original Series and recently this reasoning has been expanded by some to include all "modern Trek" series and movies.
A more extreme group of fans refuse to accept anything but The Original Series and subsequent movies featuring the original cast as canon, rejecting anything produced after TNG (or, alternately, after the death of Gene Roddenberry).
The term "personal canon" has been used to describe such selective rejection of aspects of the Star Trek franchise.
Klingon language issues
Also in the Star Trek universe, issues of what is and is not canon also are rife in the various Klingon-speaking communities.
The Klingon Language Institute takes the policy that Klingon is only canon if sanctioned by its creator, Marc Okrand; this essentially limits canon to what appears in the books The Klingon Dictionary, Klingon for the Galactic Traveller, the tapes Power Klingon and Conversational Klingon, the various movies up to and including Star Trek VI: The Undiscovered Country (Klingon in the later movies tended to be done without Okrand's involvement) and various articles in the KLI's journal, HolQeD; however, various interviews and conversations with Okrand have also been considered canon. Whether the Klingon in the novel Sarek is canon is debated, although the author, Ann C. Crispin, states in the introduction to that book that the Klingon in that book was okayed by Okrand.
Other groups have used Okrand's work and expanded upon it - for instance, Glen Proechel's Interstellar Language School - or include various other Trek novels, novellas or movies in Klingon language canon.