region vs Old World

region and Old World both are nouns.

Word	Noun	Adjective	Verb	Adverb
region	Yes	No	No	No
Old World	Yes	No	No	No

region (noun)	Old World (noun)
a part of an animal that has a special function or is supplied by a given artery or nerve	regions of the world such as Africa, Europe and Asia that were known to Europeans before the discovery of the Americas which they called the New World
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')