Nigerian vs Haussa

Nigerian and Haussa both are nouns.

Word	Noun	Adjective	Verb	Adverb
Nigerian	Yes	Yes	No	No
Haussa	Yes	No	No	No

As nouns, Haussa is a hyponym of Nigerian; that is, Haussa is a word with a more specific, narrower meaning than Nigerian:

Other hyponyms of Nigerian include Hausa, Edo, Igbo, Yoruba.

Nigerian (noun)	Haussa (noun)
a native or inhabitant of Nigeria	the chief member of the Chadic family of Afroasiatic languages; widely used as a trading language
	a member of a Negroid people living chiefly in northern Nigeria

Nigerian (adjective)	Haussa (adjective)
of or relating to the people of Nigeria
of or relating to Nigeria