Origin and Definition of the word "Canon"

"Canon" comes from the Greek word for rule or law. Musically, it designates the strictest form of counterpoint in which one voice is bound to imitate the rhythm, and interval content of another voice.

Requirements of a Canon

To qualify as a canon three conditions must be met:

1. The 2nd voice must be an exact repetition or a contrapuntal derivation of the 1st.

2. The 2nd voice must enter later than the 1st (cancrizans and proportional canon excepted)

3. The 2nd voice may not deviate from the 1st voice or its contrapuntal variations. Thus, the 2nd voice is thought to be strictly generated by the 1st. The two voices of a canon have been called dux/comes, antecedens/consequens, or proposta/ risposta; but this study uses the terms "leader" and "follower."

If all of the above conditions are met, the canon is said to be "strict." If liberties are taken with one or more of the above conditions, the canon is said to be "free." Canons of the 18th and 20th centuries tend to be strict, while canons of the 19th century may be free.

In fiction, canon is the officially authorized interpretation of characters and events. It is also sometimes described as "part of a fictional universe which has inarguable validity within". In fandom, the term is often used to distinguish between "canonical" accounts (i.e. those authorized by the copyright holder) and those of fanfiction, sometimes called fanon. In serial fiction, new material can contradict earlier material (a practice known as retconning), in which case the new material becomes canon. Publishers, especially in mainstream comic books, sometimes release "what-if" stories featuring non-canonical interpretations of their characters.