foam vs whitewater

foam and whitewater both are nouns.

Word	Noun	Adjective	Verb	Adverb
foam	Yes	No	Yes	No
whitewater	Yes	No	No	No

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

Other hyponyms of foam include shaving foam, head, lather, lather, soapsuds, suds, spume, white water.

foam (noun)	whitewater (noun)
a mass of small bubbles formed in or on a liquid	frothy water as in rapids or waterfalls
a lightweight material in cellular form; made by introducing gas bubbles during manufacture

foam (verb)	whitewater (verb)
become bubbly or frothy or foaming