friend vs companion

friend and companion both are nouns.

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

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

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

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