mummy vs mamma

mummy and mamma both are nouns.

Word	Noun	Adjective	Verb	Adverb
mummy	Yes	No	No	No
mamma	Yes	No	No	No

As nouns, mummy and mamma are synonyms defined as:

Other synonyms of mummy include ma, mama, mammy, mom, momma, mommy, mum, mumma.

mummy (noun)	mamma (noun)
a body embalmed and dried and wrapped for burial (as in ancient Egypt)	milk-secreting organ of female mammals
informal terms for a mother	informal terms for a mother