mainland China vs PRC

mainland China and PRC both are nouns.

Word	Noun	Adjective	Verb	Adverb
mainland China	Yes	No	No	No
PRC	Yes	No	No	No

As nouns, mainland China and PRC are synonyms defined as:

mainland China and PRC: a communist nation that covers a vast territory in eastern Asia; the most populous country in the world

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

mainland China (noun)	PRC (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