region vs Heaviside layer

region and Heaviside layer both are nouns.

Word	Noun	Adjective	Verb	Adverb
region	Yes	No	No	No
Heaviside layer	Yes	No	No	No

region (noun)	Heaviside layer (noun)
a part of an animal that has a special function or is supplied by a given artery or nerve	a region of the ionosphere (from 50 to 90 miles up) that reflects radio waves of medium length
a knowledge domain that you are interested in or are communicating about
the extended spatial location of something
a large indefinite location on the surface of the Earth
the approximate amount of something (usually used prepositionally as in `in the region of')