Strictly, an inscribed formula by which polyphony is derived from a single line through strict imitation at fixed or (less often) variable intervals of pitch and time; since the 16th century the term has been used for the work itself. Special types include the ‘rota’ or Round, the Cancrizans and the Mirror canon.

In the 14th century canonic writing flourished in such genres as the Caccia and the Rondellus, reaching an apex in Machaut's works. The Flemish masters of the 15th century employed it with increasing complexity, but its creative importance declined in the 16th century although its role as a subject for study began to grow. The teaching of counterpoint in the 17th century found expression in such collections as Thiele's Kunstbuch, a compendium of canonic art which points to the final phase of Bach's music. Canonic techniques had little place in the music of the symphonic era or in the Romantic period, but the neo-classical and serial schools of the 20th century have restored their place.

The word canon (or canun) was used in western Europe from the 12th century to the 14th for derivatives of the Perso-Arab plucked zither, qānūn.