sustainer vs friend

sustainer and friend both are nouns.

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

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

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

sustainer (noun)	friend (noun)
someone who upholds or maintains	a person you know well and regard with affection and trust
	a person with whom you are acquainted
	an associate who provides cooperation or assistance
	a person who backs a politician or a team etc.