girlfriend vs friend

girlfriend and friend both are nouns.

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

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

Other hypernyms of girlfriend include adult female, woman.

girlfriend (noun)	friend (noun)
a girl or young woman with whom a man is romantically involved	a person you know well and regard with affection and trust
any female friend	a person with whom you are acquainted
	an associate who provides cooperation or assistance
	a person who backs a politician or a team etc.