A doppelgänger , sometimes spelled doppelgaenger or doppelganger, is a ghostly double of a living person, especially one that haunts its own fleshly counterpart.
In fiction and mythology, a doppelgänger is often portrayed as a ghostly or paranormal phenomenon and usually seen as a harbinger of bad luck. Other traditions and stories equate a doppelgänger with an evil twin. In modern times, the term twin stranger is occasionally used.