People's Republic of China vs mainland China

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

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

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

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

Other synonyms of People's Republic of China include Cathay, China, Communist China, PRC, Red China.

People's Republic of China (noun)	mainland 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