amah vs lady's maid

amah and lady's maid both are nouns.

Word	Noun	Adjective	Verb	Adverb
amah	Yes	No	No	No
lady's maid	Yes	No	No	No

As nouns, lady's maid is a hyponym of amah; that is, lady's maid is a word with a more specific, narrower meaning than amah:

Other hyponyms of amah include chambermaid, fille de chambre, handmaid, handmaiden, parlormaid, parlourmaid.

amah (noun)	lady's maid (noun)
a female domestic	a maid who is a lady's personal attendant
a woman hired to suckle a child of someone else