mummy vs mum

mummy and mum both are nouns.

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

As nouns, mummy and mum are synonyms defined as:

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

mummy (noun)	mum (noun)
a body embalmed and dried and wrapped for burial (as in ancient Egypt)	secrecy
informal terms for a mother	informal terms for a mother
	of China

mummy (adjective)	mum (adjective)
	failing to speak or communicate etc when expected to