specter vs apparition

specter and apparition both are nouns.

Word	Noun	Adjective	Verb	Adverb
specter	Yes	No	No	No
apparition	Yes	No	No	No

As nouns, apparition is a hypernym of specter; that is, apparition is a word with a broader meaning than specter:

Other hypernyms of specter include fantasm, phantasm, phantasma, phantom, shadow.

As nouns, specter and apparition are synonyms defined as:

Other synonyms of specter include fantasm, phantasm, phantasma, phantom, spectre.

specter (noun)	apparition (noun)
a mental representation of some haunting experience	an act of appearing or becoming visible unexpectedly
a ghostly appearing figure	something existing in perception only
	the appearance of a ghostlike figure
	a ghostly appearing figure