mammy vs mum

mammy and mum both are nouns.

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

As nouns, mammy and mum are synonyms defined as:

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

mammy (noun)	mum (noun)
informal terms for a mother	secrecy
an offensive term for a Black nursemaid in the southern U.S.	informal terms for a mother
	of China

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