Honshu vs Japanese capital

Honshu and Japanese capital both are nouns.

Word	Noun	Adjective	Verb	Adverb
Honshu	Yes	No	No	No
Japanese capital	Yes	No	No	No

Honshu (noun)	Japanese capital (noun)
the central and largest of the four main islands of Japan; between the Sea of Japan and the Pacific Ocean; regarded as the Japanese mainland	the capital and largest city of Japan; the economic and cultural center of Japan