Ghost

From Hpwiki

A ghost is the non-substantial remnant of a person who died. Ghosts are more or less transparent and can pass through things like walls, floors, etc. Vice versa, objects like thrown stones pass through them like through air. Ghosts can speak, make all kinds of noises, and move or throw things.

According to common understanding, a person who dies leaves (or creates) a ghost when he/she has something left to do on earth. Reasons for staying behind include revenge (Moaning Myrtle haunting Olive Hornby), fear of death (Nearly Headless Nick) and dedication (Binns). Ghost tales are usually very sad and full of sorrow.

In the Harry Potter world, ghosts are fairly numerous, particularly in older buildings such as Hogwarts. The four house ghosts are the Bloody Baron, Nearly Headless Nick, the Grey Lady and the Fat Friar. There are many other ghosts that haunt Hogwarts, though.