rival vs enemy

rival and enemy both are nouns.

Word	Noun	Adjective	Verb	Adverb
rival	Yes	Yes	Yes	No
enemy	Yes	No	No	No

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

rival (noun)	enemy (noun)
the contestant you hope to defeat	an opposing military force
	any hostile group of people
	an armed adversary (especially a member of an opposing military force)
	a personal enemy

rival (adjective)	enemy (adjective)
as a rival in a competition

rival (verb)	enemy (verb)
be the rival of, be in competition with
be equal to in quality or ability