Use the word fandom to talk about the community of people who admire a particular celebrity, hero, sports team, or TV show. If you are president of the Boston Red Sox fan club, you're part of the team's fandom.
Your favorite boy band might have a fandom that consists mainly of screaming pre-teens, while National Public Radio's fandom is probably mostly middle aged. If you are a fan of a singer or a series of comic books, you can say you belong to their fandom. The word has been around since the very early twentieth century, from fan, a baseball slang abbreviation of fanatic, which comes from the Latin fanaticus, "mad, or inspired by a god."