guess vs opinion

guess

noun
  • A prediction about the outcome of something, typically made without factual evidence or support. 

verb
  • to suppose (introducing a proposition of uncertain plausibility). 

  • To solve by a correct conjecture; to conjecture rightly. 

  • To reach a partly (or totally) unqualified conclusion. 

  • To think, conclude, or decide (without a connotation of uncertainty). Usually in first person: "I guess". 

opinion

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

  • 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. 

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