canon — as in: played a canon
Pachelbel’s Canon in D is the most relaxing music I know.
a melody that, after a short interval, is exactly repeated by a different instrument or voice to create competing melodic lines (a strict counterpoint)
Different Christian denominations vary slightly in the "books of the Bible" they recognize as divinely inspired. Similar situations arise in other religions. The accepted works by any religious body could be referred to as their canon.
More rarely, canon references a dignitary attached to a cathedral, a collegiate church, or certain religious orders. It can also reference an unchanging part of a religious service in which bread and wine are consecrated for communion.
Canonization refers to the act of adding someone to the canon (list) of recognized saints of a Christian religious body.