public opinion vs vox populi

public opinion and vox populi both are nouns.

Word	Noun	Adjective	Verb	Adverb
public opinion	Yes	No	No	No
vox populi	Yes	No	No	No

As nouns, public opinion and vox populi are synonyms defined as:

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

Other synonyms of public opinion include opinion, popular opinion.

public opinion (noun)	vox populi (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