Cymru vs Wales

Cymru and Wales both are nouns.

Word	Noun	Adjective	Verb	Adverb
Cymru	Yes	No	No	No
Wales	Yes	No	No	No

As nouns, Cymru and Wales are synonyms defined as:

Cymru and Wales: one of the four countries that make up the United Kingdom of Great Britain and Northern Ireland; during Roman times the region was known as Cambria

Other synonyms of Cymru include Cambria.

Cymru (noun)	Wales (noun)
one of the four countries that make up the United Kingdom of Great Britain and Northern Ireland; during Roman times the region was known as Cambria	one of the four countries that make up the United Kingdom of Great Britain and Northern Ireland; during Roman times the region was known as Cambria