region vs Appleton layer

region and Appleton layer both are nouns.

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

region (noun)	Appleton layer (noun)
a part of an animal that has a special function or is supplied by a given artery or nerve	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 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')