'-dict' comes from Latin, where it has the meaning "say, speak. '
Contradict - to express the opposite of
Prediction - a statement foretelling the future
Dictate - to speak out loud for another person to write down.
Interdict - command against
Edict - a formal or authoritative proclamation
Predict - make a guess about what will happen in the future
Verdict - findings of a jury on issues submitted to it for decision
Dictator - a ruler who is unconstrained by law