Gulf of Naples vs Bay of Naples

Gulf of Naples and Bay of Naples both are nouns.

Word	Noun	Adjective	Verb	Adverb
Gulf of Naples	Yes	No	No	No
Bay of Naples	Yes	No	No	No

As nouns, Gulf of Naples and Bay of Naples are synonyms defined as:

Gulf of Naples and Bay of Naples: an arm of the Tyrrhenian Sea at Naples

Gulf of Naples (noun)	Bay of Naples (noun)
an arm of the Tyrrhenian Sea at Naples	an arm of the Tyrrhenian Sea at Naples