opponent vs opposition

opponent and opposition both are nouns.

Word	Noun	Adjective	Verb	Adverb
opponent	Yes	Yes	No	No
opposition	Yes	No	No	No

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

opponent: someone who offers opposition
opposition: an armed adversary (especially a member of an opposing military force)

Other hyponyms of opponent include dueler, duelist, dueller, duellist, enemy, foe, foeman, Luddite, withstander.

As nouns, opponent and opposition are synonyms defined as:

Other synonyms of opponent include opposite.

opponent (noun)	opposition (noun)
someone who offers opposition	the act of hostile groups opposing each other
a contestant that you are matched against	the action of opposing something that you disapprove or disagree with
	a body of people united in opposing something
	an armed adversary (especially a member of an opposing military force)
	a contestant that you are matched against
	a direction opposite to another
	the relation between opposed entities

opponent (adjective)	opposition (adjective)
characterized by active hostility