potbelly vs tummy

potbelly and tummy both are nouns.

Word	Noun	Adjective	Verb	Adverb
potbelly	Yes	No	No	No
tummy	Yes	No	No	No

As nouns, potbelly and tummy are synonyms defined as:

Other synonyms of potbelly include bay window, corporation, pot.

potbelly (noun)	tummy (noun)
a bulbous stove in which wood or coal is burned	an enlarged and muscular saclike organ of the alimentary canal; the principal organ of digestion
slang for a paunch	slang for a paunch