region vs D-layer

region and D-layer both are nouns.

Word	Noun	Adjective	Verb	Adverb
region	Yes	No	No	No
D-layer	Yes	No	No	No

region (noun)	D-layer (noun)
a part of an animal that has a special function or is supplied by a given artery or nerve	the lowest region of the ionosphere (35 to 50 miles up) that reflects low-frequency radio waves
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')