classmate vs friend

classmate and friend both are nouns.

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

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

Other hypernyms of classmate include acquaintance.

classmate (noun)	friend (noun)
an acquaintance that you go to school with	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.