Ghost:
/gost/ noun
an apparition of a dead person that is believed to appear or manifest itself to the living
A ghost story:
(i) my symptoms only existed when I stopped existing
A ghost story:
(ii) my insomnia learned to eat quickly until there was only a figment of my imagination left
A ghost story:
(iii) my dog doesn't see me when I try to pet her, and instead growls at what my mother calls "thin air"