rapid vs river

rapid and river both are nouns.

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

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

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