Singapore Island vs Singapore

Singapore Island and Singapore both are nouns.

Word	Noun	Adjective	Verb	Adverb
Singapore Island	Yes	No	No	No
Singapore	Yes	No	No	No

As nouns, Singapore Island and Singapore are synonyms defined as:

Singapore Island and Singapore: an island to the south of the Malay Peninsula

Singapore Island (noun)	Singapore (noun)
an island to the south of the Malay Peninsula	a country in southeastern Asia on the island of Singapore; achieved independence from Malaysia in 1965
	an island to the south of the Malay Peninsula
	the capital of Singapore; one of the world's biggest ports