belief vs opinion

belief

noun
  • Faith or trust in the reality of something; often based upon one's own reasoning, trust in a claim, desire of actuality, and/or evidence considered. 

  • Mental acceptance of a claim as true. 

  • Religious faith. 

  • One's religious or moral convictions. 

  • The quality or state of believing. 

  • Something believed. 

opinion

noun
  • A belief, judgment or perspective that a person has formed, either through objective or subjective reasoning, about a topic, issue, person or thing. 

  • a judicial opinion delivered by an Advocate General to the European Court of Justice where he or she proposes a legal solution to the cases for which the court is responsible 

  • The formal decision, or expression of views, of a judge, an umpire, a doctor, or other party officially called upon to consider and decide upon a matter or point submitted. 

  • The judgment or sentiment which the mind forms of persons or things; estimation. 

How often have the words belief and opinion occurred in a corpus of books? (source: Google Ngram Viewer )