paunch vs tummy

paunch and tummy both are nouns.

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

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

Other hyponyms of paunch include bay window, corporation, pot, potbelly.

paunch (noun)	tummy (noun)
a protruding abdomen	an enlarged and muscular saclike organ of the alimentary canal; the principal organ of digestion
	slang for a paunch