heathen vs ethnic

heathen and ethnic both are nouns.

Word	Noun	Adjective	Verb	Adverb
heathen	Yes	Yes	No	No
ethnic	Yes	Yes	No	No

As adjectives, heathen and ethnic are synonyms defined as:

heathen and ethnic: not acknowledging the God of Christianity and Judaism and Islam

Other synonyms of heathen include heathenish, pagan.

heathen (noun)	ethnic (noun)
a person who does not acknowledge your god	a person who is a member of an ethnic group

heathen (adjective)	ethnic (adjective)
not acknowledging the God of Christianity and Judaism and Islam	not acknowledging the God of Christianity and Judaism and Islam
	denoting or deriving from or distinctive of the ways of living built up by a group of people