foam vs soapsuds

foam and soapsuds both are nouns.

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

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

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

foam (noun)	soapsuds (noun)
a mass of small bubbles formed in or on a liquid	the froth produced by soaps or detergents
a lightweight material in cellular form; made by introducing gas bubbles during manufacture

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