Appleton layer vs region

Appleton layer and region both are nouns.

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

Appleton layer (noun)	region (noun)
the highest region of the ionosphere (from 90 to 600 miles up) which contains the highest concentration of free electrons and is most useful for long-range radio transmission	a part of an animal that has a special function or is supplied by a given artery or nerve
	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')