Phantasm
Part of speech: noun
Definition: something seen but having no physical reality; a phantom or apparition
Phantom
Part of speech: noun
Definition: Something apparently seen, heard, or sensed, but having no physical reality; a ghost or apparition; something elusive or delusive.An image that appears only in the mind; an illusion.
Part of speech: adjective
Definition: illusivefictitious or nonexistent
Example sentence: Art has a double face, of expression and illusion, just like science has a double face: the reality of error and the phantom of truth.