Level of Distractibility: Who cares? = *. Some people will be distracted from your meaning = **. Many people will be distracted from your meaning = ***.
Question: I keep confusing the spelling of "cannon" with "canon." What is "canon" anyhow?
Answer: "Cannon" is artillery. It has two "n's."
The most frequent use of "canon" today is with literature: the "canon" is a list of literary works that experts believe to be the best that has been written. In short, they are the classics of literature. If you check the dictionary definition of "canon," you will find it related to works in the Christian religion and to law ("canon law"). But today you are most likely to hear the word in reference to the accepted classics in literature.
Rating of Distractibility: ***. Since the words have no relationship in meaning, people are likely to recognize the misuse of one for the other.