messmate vs friend

messmate and friend both are nouns.

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

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

messmate: (nautical) an associate with whom you share meals in the same mess (as on a ship)
friend: a person with whom you are acquainted

Other hypernyms of messmate include acquaintance.

messmate (noun)	friend (noun)
(nautical) an associate with whom you share meals in the same mess (as on a ship)	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.