ghost word vs signifier

ghost word and signifier both are nouns.

Word	Noun	Adjective	Verb	Adverb
ghost word	Yes	No	No	No
signifier	Yes	No	No	No

As nouns, signifier is a hypernym of ghost word; that is, signifier is a word with a broader meaning than ghost word:

ghost word: a word form that has entered the language through the perpetuation of an error
signifier: the phonological or orthographic sound or appearance of a word that can be used to describe or identify something

Other hypernyms of ghost word include descriptor, form, word form.

ghost word (noun)	signifier (noun)
a word form that has entered the language through the perpetuation of an error	the phonological or orthographic sound or appearance of a word that can be used to describe or identify something