city vs Byzantium

city and Byzantium both are nouns.

Word	Noun	Adjective	Verb	Adverb
city	Yes	No	No	No
Byzantium	Yes	No	No	No

city (noun)	Byzantium (noun)
people living in a large densely populated municipality	an ancient city on the Bosporus founded by the Greeks; site of modern Istanbul; in 330 Constantine I rebuilt the city and called it Constantinople and made it his capital
a large and densely populated urban area; may include several independent administrative districts	a continuation of the Roman Empire in the Middle East after its division in 395
an incorporated administrative district established by state charter