aftertaste vs afterimage

aftertaste and afterimage both are nouns.

Word	Noun	Adjective	Verb	Adverb
aftertaste	Yes	No	No	No
afterimage	Yes	No	No	No

As nouns, afterimage is a hypernym of aftertaste; that is, afterimage is a word with a broader meaning than aftertaste:

aftertaste: an afterimage of a taste
afterimage: an image (usually a negative image) that persists after stimulation has ceased

Other hypernyms of aftertaste include aftersensation.

aftertaste (noun)	afterimage (noun)
an afterimage of a taste	an image (usually a negative image) that persists after stimulation has ceased