bubble vs foam

bubble and foam both are nouns.

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

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

Other hyponyms of bubble include air bubble, froth, soap bubble.

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

Other hyponyms of bubble include effervesce, fizz, form bubbles, froth, sparkle.

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

bubble (verb)	foam (verb)
expel gas from the stomach	become bubbly or frothy or foaming
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