river vs rapid

river and rapid both are nouns.

Word	Noun	Adjective	Verb	Adverb
river	Yes	No	No	No
rapid	Yes	Yes	No	No

river (noun)	rapid (noun)
a large natural stream of water (larger than a creek)	a part of a river where the current is very fast

river (adjective)	rapid (adjective)
	done or occurring in a brief period of time
	characterized by speed; moving with or capable of moving with high speed