popular opinion vs public opinion

popular opinion and public opinion both are nouns.

Word	Noun	Adjective	Verb	Adverb
popular opinion	Yes	No	No	No
public opinion	Yes	No	No	No

As nouns, popular opinion and public opinion are synonyms defined as:

popular opinion and public opinion: a belief or sentiment shared by most people; the voice of the people

Other synonyms of popular opinion include opinion, vox populi.

popular opinion (noun)	public opinion (noun)
a belief or sentiment shared by most people; the voice of the people	a belief or sentiment shared by most people; the voice of the people