Ghost, spectre, spirit, all refer to the disembodied soul of a person.
A ghost is the soul or spirit of a deceased person, which appears or otherwise makes its presence known to the living: the ghost of a drowned child. Also revenant, literally one who returns.
A spectre is a ghost or apparition of more or less weird, unearthly, or terrifying aspect: a frightening spectre. Also spook, phantom, phantasm...
Spirit is often interchangeable with ghost but may mean a supernatural being, usually with an indication of good or malign intent toward human beings: the spirit of a friend; an evil spirit.
A doppelganger is a ghostly double or counterpart of a living person.
Shade suggests a shadow or shadowy form.
A wraith is a visible spirit, sometimes an apparition of a living person, supposed to portend their death.
A poltergeist manifests its presence by noises and knockings, while a banshee, in Irish folklore, is a spirit in the form of a wailing woman who appears to, or is heard by, members of a family as a sign that one of them is about to die.
A dybbuk, according to Jewish folklore, is a demon or soul of a dead person that enters the body of a living person and directs their conduct.
A zombie is a dead body given the semblance of life by a supernatural force, usually for evil purpose.
A ghoul is an evil demon supposed to feed on humans, especially by robbing graves and feeding on corpses.