Canon usually means the body of poems, poets, or literary works that a culture, school, or critic treats as especially important, influential, or worth studying. It is not fixed: the canon can change as tastes, values, and institutions change.
The word can also refer to a strict imitative poetic form, but that meaning is less common than the idea of an accepted body of literature.
Example
The class traced how the canon shifted over time:
first the old masters,
then voices once left outside the list,
finally poets readers had ignored for years.
[n] a collection of books accepted as holy scripture especially the books of the Bible recognized by any Christian church as genuine and inspired
[n] a complete list of saints that have been recognized by the Roman Catholic Church
[n] a rule or especially body of rules or principles generally established as valid and fundamental in a field or art or philosophy; "the neoclassical canon"; "canons of polite society"
[n] a contrapuntal piece of music in which a melody in one part is imitated exactly in other parts
[n] (North America) a ravine formed by a river in an area with little rainfall
[n] a priest who is a member of a cathedral chapter