imaginary
Existing only in the imagination.
Example
“Unicorns are imaginary.”
Other meanings
Having no real part; that part of a complex number which is a multiple of \sqrt{-1} (called imaginary unit).
Word history
From Latin "imāginārius" (relating to images, fancied).
Where this comes from
This definition is adapted from “imaginary” on Wiktionary, by its contributors, published under CC BY-SA 4.0. This page is published under the same licence.