friend vs class fellow

friend and class fellow both are nouns.

Word	Noun	Adjective	Verb	Adverb
friend	Yes	No	No	No
class fellow	Yes	No	No	No

As nouns, class fellow is a hyponym of friend; that is, class fellow is a word with a more specific, narrower meaning than friend:

friend (noun)	class fellow (noun)
a person you know well and regard with affection and trust	an acquaintance that you go to school with
a person with whom you are acquainted
an associate who provides cooperation or assistance
a person who backs a politician or a team etc.