island vs Bioko

island and Bioko both are nouns.

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

island (noun)	Bioko (noun)
a zone or area resembling an island	an island in the Gulf of Guinea that is part of Equatorial Guinea
a land mass (smaller than a continent) that is surrounded by water