island vs Honshu

island and Honshu both are nouns.

Word	Noun	Adjective	Verb	Adverb
island	Yes	No	No	No
Honshu	Yes	No	No	No

island (noun)	Honshu (noun)
a zone or area resembling an island	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
a land mass (smaller than a continent) that is surrounded by water