hemisphere vs geographical area

hemisphere and geographical area both are nouns.

Word	Noun	Adjective	Verb	Adverb
hemisphere	Yes	No	No	No
geographical area	Yes	No	No	No

As nouns, geographical area is a hypernym of hemisphere; that is, geographical area is a word with a broader meaning than hemisphere:

Other hypernyms of hemisphere include geographic area, geographic region, geographical region.

hemisphere (noun)	geographical area (noun)
either half of the cerebrum	a demarcated area of the Earth
half of the terrestrial globe
half of a sphere