Doppelgänger
A doppelganger in English is an uncanny double of a person, either real or imagined. The anglicised word rhymes with banger, but in the original German word ‘Doppelgänger’ the letter ä (referred to in English as ‘a umlaut’) is pronounced to sound like the e in the word ‘length’.
A Doppelgänger may be an unseen shadow or an actual entity, an example of being in two places at once, which is termed Bilocation. The word is sometimes jokingly used to refer to a person so similar in appearance they could be taken as a copy of another, and in fiction this can be a dark and threatening figure. Famous literary doppelgangers are well described in the article “True Stories of Doppelgangers“.