Paracosm

A paracosm is an imagined, detailed fantasy world invented by a child or perhaps an adult, involving humans and/or animals, or perhaps even fantasy or alien creations. Often having its own geography, history, and language, it is an experience that continues over a long period of time: months or even years.

The concept was first described by a researcher for the BBC, Robert Silvey, with later research by British psychiatrist Stephen A. MacKeith, and British psychologist David Cohen.

Silvey & MacKeith published The Paracosm: a special form of fantasy in 1988, and Cohen & MacKeith published The Development of Imagination: The Private Worlds of Childhood in 1991.

Probably the most famous examples of a paracosm are "Gondal", "Angria" and "Gaaldine" created by Emily, Anne, and Charlotte Brontë, and their brother Branwell.