Sub-Saharan Africa vs geographic area

Sub-Saharan Africa and geographic area both are nouns.

Word	Noun	Adjective	Verb	Adverb
Sub-Saharan Africa	Yes	No	No	No
geographic area	Yes	No	No	No

Sub-Saharan Africa (noun)	geographic area (noun)
the region of Africa to the south of the Sahara Desert	a demarcated area of the Earth