A
fictional currency is some form of defined or alluded
currency in works of
fiction. The names of such units of currency are sometimes based on extant or historic currencies (e.g. "Altairian dollars" or "Earth yen") while others, such as "Kalganids" in
Asimov's
Foundation series, may be wholly invented. A particularly common type, especially in
science fiction, is
electronically managed "credits". In some works of fiction, exchange media other than money are used. These are not currency as such, but rather nonstandard
media of exchange used to avoid the difficulties of ensuring "
double coincidence of wants" in a
barter system.
