Controversy is a state of prolonged public dispute or debate, usually concerning a matter of opinion. The word was coined from the Latin controversia, as a composite of controversus – "turned in an opposite direction," from contra – "against" – and vertere – to turn, or versus (see verse), hence, "to turn against."
Perennial areas of controversy include history, religion, philosophy and politics. Other minor areas of controversy may include economics, science, finances, organisation, age, gender, and race. Controversy in matters of theology has traditionally been particularly heated, giving rise to the phrase odium theologicum. Controversial issues are held as potentially divisive in a given society, because they can lead to tension and ill will, as a result they are often taboo to be discussed in the light of company in many cultures.
In the theory of law, a controversy differs from a legal case; while legal cases include all suits, criminal as well as civil, a controversy is a purely civil proceeding.
For example, the Case or Controversy Clause of Article Three of the United States Constitution (Section 2, Clause 1) states that "the judicial Power shall extend ... to Controversies to which the United States shall be a Party". This clause has been deemed to impose a requirement that United States federal courts are not permitted to hear cases that do not pose an actual controversy—that is, an actual dispute between adverse parties which is capable of being resolved by the court. In addition to setting out the scope of the jurisdiction of the federal judiciary, it also prohibits courts from issuing advisory opinions, or from hearing cases that are either unripe, meaning that the controversy has not arisen yet, or moot, meaning that the controversy has already been resolved.