Pacific Ocean vs Japanese Islands

Pacific Ocean and Japanese Islands both are nouns.

Word	Noun	Adjective	Verb	Adverb
Pacific Ocean	Yes	No	No	No
Japanese Islands	Yes	No	No	No

Pacific Ocean (noun)	Japanese Islands (noun)
the largest ocean in the world	a string of more than 3,000 islands to the east of Asia extending 1,300 miles between the Sea of Japan and the western Pacific Ocean