Canon

The term Canon is of Latin origin and refers to the source material. In The Legend of Zelda, it means anything which has been established as fact by official sources, most particularly the games themselves and their manuals. It is canonical fact, for example, that all daughters born in the royal family of Hyrule are to be named Zelda; this was established in the backstory for Zelda II: The Adventure of Link.

Certain statements are regarded as canon by some players but not by others. For instance, in an interview, Zelda's creator stated that The Legend of Zelda: Ocarina of Time comes before any of the others chronologically. Because this has not been formally established within the games themselves, however, some players view this "fact" with a jaundiced eye.

The Zelda series is perhaps unique in that its canon has been known, at times, to contradict itself; for example, the map of Hyrule has been known to change from one game to another. This makes it difficult, if not outright impossible, for some facts to be concretely established in a manner which satisfies everyone.

See also Timeline, fanon, and Wikipedia's entry on canon.