Solomon Islands vs Bougainville

Solomon Islands and Bougainville both are nouns.

Word	Noun	Adjective	Verb	Adverb
Solomon Islands	Yes	No	No	No
Bougainville	Yes	No	No	No

Solomon Islands (noun)	Bougainville (noun)
the southern Solomon Islands that since 1978 form an independent state in the British Commonwealth	the largest of the Solomon Islands; a province of Papua New Guinea
the northernmost islands are part of Papua New Guinea; the remainder form an independent state within the British Commonwealth	French explorer who circumnavigated the globe accompanied by scientists (1729-1811)