Houston vs city

Houston and city both are nouns.

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

Houston (noun)	city (noun)
the largest city in Texas; located in southeastern Texas near the Gulf of Mexico; site of the National Aeronautics and Space Administration	people living in a large densely populated municipality
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)	a large and densely populated urban area; may include several independent administrative districts
	an incorporated administrative district established by state charter