noun

• (Roman law) A rent or stipend payable at some regular time, generally annual, e.g., canon frumentarius
  "The lessees of public lands had to pay a perpetual rent or "canon" at some periodical time."
• (chiefly fandom slang, uncountable) Those sources, especially including literary works, which are considered part of the main continuity regarding a given fictional universe; (metonymic) these sources' content.
  "A spin-off book series revealed the aliens to be originally from Earth, but it's not canon."
• (cooking) Alternative form of cannon (“rolled and filleted loin of meat”).
  "a canon of beef or lamb"
• (printing, dated, uncountable) A large size of type formerly used for printing the church canons, standardized as 48-point.

adj

• (fandom slang) Clipping of canonical.
  "The franchise's book spinoff is usually not considered canon."

noun

• (obsolete, now a misspelling) Alternative spelling of cannon (“weapon”).

name

• (Roman Catholicism, with definite article) The Canon of the Mass.