Paracosm

The creator of a paracosm has a complex and deeply felt relationship with this subjective universe, which may incorporate real-world or imaginary characters and conventions.

Commonly having its own geography, history, and language, it is an experience that is often developed during childhood and continues over a long period of time, months or even years, as a sophisticated reality that can last into adulthood.

[6] In Adam Gopnik's essay "Bumping Into Mr. Ravioli", he consults his sister, a child psychologist, about his three-year-old daughter's imaginary friend.

A Michigan State University study undertaken by Root-Bernstein revealed that many MacArthur Fellows Program recipients had paracosms as children, thus engaging in what she calls worldplay.

[4] Paracosms are one of the subjects of interest to the emerging field of literary juvenilia, studying the childhood writings of well-known and lesser-known authors.