companion vs friend

companion and friend both are nouns.

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

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

companion (noun)	friend (noun)
a friend who is frequently in the company of another	a person you know well and regard with affection and trust
one paid to accompany or assist or live with another	a person with whom you are acquainted
a traveler who accompanies you	an associate who provides cooperation or assistance
	a person who backs a politician or a team etc.

companion (verb)	friend (verb)
be a companion to somebody