ma'am vs grande dame

ma'am and grande dame both are nouns.

Word	Noun	Adjective	Verb	Adverb
ma'am	Yes	No	No	No
grande dame	Yes	No	No	No

As nouns, grande dame is a hyponym of ma'am; that is, grande dame is a word with a more specific, narrower meaning than ma'am:

ma'am: a woman of refinement
grande dame: a middle-aged or elderly woman who is stylish and highly respected

ma'am (noun)	grande dame (noun)
a woman of refinement	a middle-aged or elderly woman who is stylish and highly respected