Bay of Naples vs Gulf of Naples

Bay of Naples and Gulf of Naples both are nouns.

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

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

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

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