au pair vs noncitizen

au pair and noncitizen both are nouns.

Word	Noun	Adjective	Verb	Adverb
au pair	Yes	No	No	No
noncitizen	Yes	No	No	No

As nouns, noncitizen is a hypernym of au pair; that is, noncitizen is a word with a broader meaning than au pair:

au pair: a young foreigner who lives with a family in return for doing light housework
noncitizen: a person who comes from a foreign country; someone who does not owe allegiance to your country

Other hypernyms of au pair include alien, foreigner, outlander.

au pair (noun)	noncitizen (noun)
a young foreigner who lives with a family in return for doing light housework	a person who comes from a foreign country; someone who does not owe allegiance to your country