Fandom is the loosely organized realm of the science fiction fans. “Fan” has a special meaning when applied to the science fiction field, where it is not to be taken in the loose sense of the aficianado, although that is an original synonym. A science fiction fan is not merely one who observes, who watches, no matter how worshipfully and attentively, as may be the case with a sports fan or a fan of popular music or a devotee of the works of Agatha Christie. SF fandom is made up of people engaging in one or more of the following activities: participating in local science fiction clubs or discussion groups; writing letters to magazines that publish SF; writing letters to other SF fans; attending regional or national SF conventions; collecting SF or related materials; publishing or participating in amateur publications about SF; publishing or participating in publications about SF fandom (not necessarily about science fiction directly).
A person who reads only SF, even if he or she reads a great deal of it, but does not engage in any of these activities is not part of the world of fandom and for the sake of clarity will be referred to as an SF reader rather than a fan. The great majority of SF readers—including most omnivores and chronics—in this strict sense are not fans.
Fans make up only a small part, perhaps 5 percent, or the SF audience. However, they play a central and crucial role in making the SF field what it is. Without fandom, SF might never have established itself as a genre, might well have perished long ago. The activities of fans have kept it alive and vigorous. (147–48)
What motivates the fan, the point of fan activity, is the construction, finishing, and exhibiting of a fan persona through collecting, convention appearances, and writings and other active contributions to the publishing of fanzines. What makes the development of this persona possible is the fact that fandom is a microcosm, a private, limited world with its own rules and mores, small enough so that some sense of belonging is within the reach of every fan who wants to be a part of it. (167)
—David Hartwell, Age of Wonders: Exploring the World of Science Fiction (New York: Walker, 1984)