tum vs tummy

tum and tummy both are nouns.

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

As nouns, tum and tummy are synonyms defined as:

tum and tummy: an enlarged and muscular saclike organ of the alimentary canal; the principal organ of digestion

Other synonyms of tum include breadbasket, stomach.

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