Yuman vs Yuma

Yuman and Yuma both are nouns.

Word	Noun	Adjective	Verb	Adverb
Yuman	Yes	Yes	No	No
Yuma	Yes	No	No	No

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

Yuman: a group of language of the Hokan family in Arizona and California and Mexico
Yuma: the Yuman language spoken by the Yuma

Yuman (noun)	Yuma (noun)
a group of language of the Hokan family in Arizona and California and Mexico	the Yuman language spoken by the Yuma
	a town in southwestern Arizona on the Colorado River and the California border
	a member of the North American Indian people of Arizona and adjacent Mexico and California

Yuman (adjective)	Yuma (adjective)
of or relating to the language or culture of the Yuma people