Houston vs urban center

Houston and urban center both are nouns.

Word	Noun	Adjective	Verb	Adverb
Houston	Yes	No	No	No
urban center	Yes	No	No	No

Houston (noun)	urban center (noun)
the largest city in Texas; located in southeastern Texas near the Gulf of Mexico; site of the National Aeronautics and Space Administration	a large and densely populated urban area; may include several independent administrative districts
United States politician and military leader who fought to gain independence for Texas from Mexico and to make it a part of the United States (1793-1863)