Madras vs Chennai

Madras and Chennai both are nouns.

Word	Noun	Adjective	Verb	Adverb
Madras	Yes	No	No	No
Chennai	Yes	No	No	No

As nouns, Madras and Chennai are synonyms defined as:

Madras and Chennai: a city in Tamil Nadu on the Bay of Bengal; formerly Madras

Madras (noun)	Chennai (noun)
a city in Tamil Nadu on the Bay of Bengal; 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