Singapore vs capital of Singapore

Singapore and capital of Singapore both are nouns.

Word	Noun	Adjective	Verb	Adverb
Singapore	Yes	No	No	No
capital of Singapore	Yes	No	No	No

As nouns, Singapore and capital of Singapore are synonyms defined as:

Singapore and capital of Singapore: the capital of Singapore; one of the world's biggest ports

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