a term used in fanfiction to describe commonly accepted ideas among authors even if they are not actually expressed in the canon
In Harry Potter, SiriusxLupin is virtually fanon.
The canon of fandom.
Fanon is the collection concepts and ideas that are normally used in most fan fiction, but don't really existence in the real story's canon.
If a concept was used in the canon, it is only mention once in the entire series and is never mentioned again. Fan fiction writers will most likely instigate these concepts in their fics.
Some people think that fanon is phoney and stupid, but most fanon concepts are actually pretty good.
often connect to fan fiction; ideas or events that are accepted by most fans, but were not actually in the original story/book/show etc.
In Death Note fanfics, Matt and Mello are often a fanon pairing.