The Desert Mermaid

There's also the matter of subtypes. Well, with ghouls its more of a matter that no one could agree on the exact definition, because they never got very far out of mythology. Ghosts, on the other hand, have a rich and concrete parascience built around them, mostly by people like ghost hunters who investigate reported hauntings. There are at least two basic types of ghosts (residual and intelligent) which have different behaviours based on their circumstances, and a number of other things which can cause hauntings (poltergeisting, spirits and demons mostly). So it's not surprising that people have a vague idea what entails either concept.