ghost is ambiguous term, it's a term used more by nonbelievers or paranormal ghostbusters who doesn't understand the concept of it quiet well
ghost is more like energy (its consciousness) floating in non-visible astral realm who's likely to be lost and looking or screaming for help, and want to be noticed
You shall not know if paranormal is real unless you see it yourself (That is be it yourself.) Which brings us to another question: Does a ghost knows it's a ghost?