Indian Ocean vs Gulf of Aden

Indian Ocean and Gulf of Aden both are nouns.

Word	Noun	Adjective	Verb	Adverb
Indian Ocean	Yes	No	No	No
Gulf of Aden	Yes	No	No	No

Indian Ocean (noun)	Gulf of Aden (noun)
the 3rd largest ocean; bounded by Africa on the west, Asia on the north, Australia on the east and merging with the Antarctic Ocean to the south	arm of the Indian Ocean at the entrance to the Red Sea