foam vs bubble

foam and bubble both are nouns.

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

As nouns, bubble is a hypernym of foam; that is, bubble is a word with a broader meaning than foam:

As verbs, bubble is a hypernym of foam; that is, bubble is a word with a broader meaning than foam:

foam (noun)	bubble (noun)
a mass of small bubbles formed in or on a liquid	a dome-shaped covering made of transparent glass or plastic
a lightweight material in cellular form; made by introducing gas bubbles during manufacture	an impracticable and illusory idea
	a speculative scheme that depends on unstable factors that the planner cannot control
	a hollow globule of gas (e.g., air or carbon dioxide)

foam (verb)	bubble (verb)
become bubbly or frothy or foaming	expel gas from the stomach
	form, produce, or emit bubbles
	cause to form bubbles
	rise in bubbles or as if in bubbles
	flow in an irregular current with a bubbling noise