urban center vs Sioux City

urban center and Sioux City both are nouns.

Word	Noun	Adjective	Verb	Adverb
urban center	Yes	No	No	No
Sioux City	Yes	No	No	No

urban center (noun)	Sioux City (noun)
a large and densely populated urban area; may include several independent administrative districts	a city in northeastern Iowa where the Big Sioux River joins the Missouri