Tamil Nadu vs Madras

Tamil Nadu and Madras both are nouns.

Word	Noun	Adjective	Verb	Adverb
Tamil Nadu	Yes	No	No	No
Madras	Yes	No	No	No

As nouns, Tamil Nadu and Madras are synonyms defined as:

Tamil Nadu and Madras: a state in southeastern India on the Bay of Bengal (south of Andhra Pradesh); formerly Madras

Tamil Nadu (noun)	Madras (noun)
a state in southeastern India on the Bay of Bengal (south of Andhra Pradesh); formerly Madras	a city in Tamil Nadu on the Bay of Bengal; formerly Madras
	a state in southeastern India on the Bay of Bengal (south of Andhra Pradesh); formerly Madras