An Etymological Dictionary of Astronomy and Astrophysics

1. A belief or judgment that rests on grounds insufficient to produce complete certainty.
   

2. A personal view, attitude, or appraisal.
   

3. Law: The formal statement by a judge or court of the reasoning and the principles of law used in reaching a decision of a case (Dictionary.com).

Etymology (EN): M.E., from O.Fr., from L. opinion- “opinion, conjecture; appreciation,” from opinari “to think, judge, suppose,” from PIE *op- “to choose.”

Etymology (PE): Pažân, from Pashto pažân / pêžân, from prefix- pa-, originally *pati-, + žân variant of Pers. dân-, dânestan “to know,” zân as in farzâne “intelligent, wise;” Balochi zân, Kurd. zân “to know;” cf. Sogd. patzân, Khotanese paysân- “to know;” Yidgha and Munji vəzân “to know;” Yizghulami vəzan, Yaghnobi bīzon, Sarigholi pajan, Ormuri pazán “to know;” Av. paiti-zan- “to recognize, acknowledge, appreciate;” from prefix paiti- + zan- “to know, have knowledge;”
Mod.Pers. dân-, dânestan “to know,” variant šenâxtan “to know, recognize,” → science.