Riga vs capital of Latvia

Riga and capital of Latvia both are nouns.

Word	Noun	Adjective	Verb	Adverb
Riga	Yes	No	No	No
capital of Latvia	Yes	No	No	No

As nouns, Riga and capital of Latvia are synonyms defined as:

Riga and capital of Latvia: a port city on the Gulf of Riga that is the capital and largest city of Latvia; formerly a member of the Hanseatic League

Riga (noun)	capital of Latvia (noun)
a port city on the Gulf of Riga that is the capital and largest city of Latvia; formerly a member of the Hanseatic League	a port city on the Gulf of Riga that is the capital and largest city of Latvia; formerly a member of the Hanseatic League