Athens vs Greek capital

Athens and Greek capital both are nouns.

Word	Noun	Adjective	Verb	Adverb
Athens	Yes	No	No	No
Greek capital	Yes	No	No	No

As nouns, Athens and Greek capital are synonyms defined as:

Athens and Greek capital: the capital and largest city of Greece; named after Athena (its patron goddess)

Other synonyms of Athens include Athinai, capital of Greece.

Athens (noun)	Greek capital (noun)
the capital and largest city of Greece; named after Athena (its patron goddess)	the capital and largest city of Greece; named after Athena (its patron goddess)
a university town in northeast Georgia
a town in southeast Ohio