Nilo-Saharan vs Songhai

Nilo-Saharan and Songhai both are nouns.

Word	Noun	Adjective	Verb	Adverb
Nilo-Saharan	Yes	No	No	No
Songhai	Yes	No	No	No

As nouns, Songhai is a hyponym of Nilo-Saharan; that is, Songhai is a word with a more specific, narrower meaning than Nilo-Saharan:

Nilo-Saharan: a family of East African languages spoken by Nilotic peoples from the Sahara south to Kenya and Tanzania
Songhai: a Nilo-Saharan language spoken by the Songhai in Mali and Niger

Other hyponyms of Nilo-Saharan include Chari-Nile, Saharan, Saharan language, Songhai language.

Nilo-Saharan (noun)	Songhai (noun)
a family of East African languages spoken by Nilotic peoples from the Sahara south to Kenya and Tanzania	a Nilo-Saharan language spoken by the Songhai in Mali and Niger