Canon and cannon sound the same, but they mean very different things.
Canon usually refers to a rule, a standard, or a group of works accepted as authentic or important. You will often see it in writing about religion, literature, film, and art. For example, you might say, This poem is part of the literary canon. In fan discussions, people also use it to mean something officially true in a story world.
Cannon is a noun for a large gun, usually mounted and used in warfare. For example, The fort still has an old cannon by the gate.
A quick way to remember the difference is this: cannon has an extra n, and it refers to something big and heavy. Canon is the spelling for authority, standards, and accepted works.
- Use canon for rules, standards, and official works.
- Use cannon for the weapon.
- Example: The sequel is not canon, but the castle still has a cannon on display.
If you are writing about books, beliefs, or official story details, choose canon. If you mean artillery, choose cannon.