Canonical \kuh-NON-i-kuhl\ , adjective;
1. Authorized; recognized; accepted
2. Included in the canon of the Bible
3. Mathematics: In simplest or standard form (of an equation, coordinate, etc.)
This word dates to the early 15th century from Middle Latin canonicalis, which comes from Late Latin canonicus ("clergyman living under a rule"), which is based on the Latin adjective canonicus ("according to rule" or "pertaining to the (Biblical) canon"). All Latin forms ultimately derive from Greek kanon ("any straight rod or bar; rule; standard of excellence").
An earlier form, canonial, is first attested in the early 13th century.
Today's word and the first definition were both taken from Dictionary.com's 'Word of the Day' for Monday, July 18
Etymologies come from the Oxford English Dictionary and/or Etymonline.com