Galveston Bay vs Gulf of Mexico

Galveston Bay and Gulf of Mexico both are nouns.

Word	Noun	Adjective	Verb	Adverb
Galveston Bay	Yes	No	No	No
Gulf of Mexico	Yes	No	No	No

Galveston Bay (noun)	Gulf of Mexico (noun)
an arm of the Gulf of Mexico in Texas to the south of Houston	an arm of the Atlantic to the south of the United States and to the east of Mexico