Fan fiction (alternately referred to as fanfiction, fanfic, FF, or fic) is a broadly-defined term used to describe stories about characters or settings written by fans of the original work, rather than by the original creator. Works of fan fiction are rarely commissioned or authorized by the original work's owner, creator, or publisher; also, they are almost never professionally published. Fan fiction, therefore, is defined by being both related to its subject's canonical fictional universe and simultaneously existing outside the canon of that universe. Most fan fiction writers assume that their work is read primarily by other fans, and therefore tend to presume that their readers have knowledge of the canon universe (created by a professional writer) in which their works are based.