Cathay vs People's Republic of China

Cathay and People's Republic of China both are nouns.

Word	Noun	Adjective	Verb	Adverb
Cathay	Yes	No	No	No
People's Republic of China	Yes	No	No	No

As nouns, Cathay and People's Republic of China are synonyms defined as:

Cathay and People's Republic of China: a communist nation that covers a vast territory in eastern Asia; the most populous country in the world

Other synonyms of Cathay include China, Communist China, mainland China, PRC, Red China.

Cathay (noun)	People's Republic of China (noun)
a communist nation that covers a vast territory in eastern Asia; the most populous country in the world	a communist nation that covers a vast territory in eastern Asia; the most populous country in the world