precedent

noun
  1. An earlier event or action that is regarded as an example or guide to be considered in subsequent similar circumstances. noun
    The court's decision set a precedent for future cases of a similar nature.
    There is no precedent for such an unusual request in our company's history.
  2. A legal decision or form of proceeding serving as an authoritative rule or pattern in future similar or analogous cases. noun
    The judge cited a precedent from a previous ruling to justify his decision.
    Lawyers often look for precedents to support their arguments in court.