Canon: (n) In the context of story franchises, canon is the official accepted story on which third-party material is judged. If something is non-canon, for example, that means it goes against what is officially established or it won't be considered to be part of the actual story. Fanfics are non-canon by their very nature, for example.

Cannon: (n) a combat weapon that is used to fire large ballistic projectiles. I.E., the cannons on a battleship, a classic colonial cannonball cannon, or a handcannon (which is slang for a remarkably large handgun).

Please to be not mixing these terms up kthxbai