Imagination
From the Simple English Wikipedia, the free encyclopedia that anyone can change
Imagination has to be primarily with the mind. It is the ability to form mental images of things or events. When someone imagines something he or she is trying to picture something in his/her mind that he/she has not experienced him/herself in reality.
The word Imaginary is also used to describe something that you have Imagined in your Imagination.
This is a very common word in English.