Speaking of what has not yet happened, and turning out right. Prophecy is recognised only afterward.
Greek prophētēs (foreteller, one who speaks for another): pro- (before) + phēmi (to speak); to be prophetic is to have spoken before the event and to have turned out right, which the speaking itself could never guarantee.
Speaking of what has not yet happened and being proven right by it. The word rewards the outcome, not the confidence of the speaker at the time of speaking.