believer vs friend

believer and friend both are nouns.

Word	Noun	Adjective	Verb	Adverb
believer	Yes	No	No	No
friend	Yes	No	No	No

As nouns, friend is a hypernym of believer; that is, friend is a word with a broader meaning than believer:

Other hypernyms of believer include admirer, booster, champion, protagonist, supporter.

believer (noun)	friend (noun)
a person who has religious faith	a person you know well and regard with affection and trust
a supporter who accepts something as true	a person with whom you are acquainted
	an associate who provides cooperation or assistance
	a person who backs a politician or a team etc.