girlfriend vs girl

girlfriend and girl both are nouns.

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

As nouns, girlfriend and girl are synonyms defined as:

girlfriend and girl: a girl or young woman with whom a man is romantically involved

Other synonyms of girlfriend include lady friend.

girlfriend (noun)	girl (noun)
a girl or young woman with whom a man is romantically involved	a young female
any female friend	a girl or young woman with whom a man is romantically involved
	a youthful female person
	a friendly informal reference to a grown woman
	a female human offspring