friend vs proponent

friend and proponent both are nouns.

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

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

Other hypernyms of friend include advocate, advocator, exponent.

friend (noun)	proponent (noun)
a person you know well and regard with affection and trust	a person who pleads for a cause or propounds an idea
a person with whom you are acquainted
an associate who provides cooperation or assistance
a person who backs a politician or a team etc.