Ground Zero vs New York City

Ground Zero and New York City both are nouns.

Word	Noun	Adjective	Verb	Adverb
Ground Zero	Yes	No	No	No
New York City	Yes	No	No	No

Ground Zero (noun)	New York City (noun)
the site of the World Trade Center before it was destroyed	the largest city in New York State and in the United States; located in southeastern New York at the mouth of the Hudson river; a major financial and cultural center