Heisenberg uncertainty principle
Named for Werner Heisenberg, its discoverer, translated into English from a variety of original German terms. Heisenberg originally called the concept Ungenauigkeit (inexactness) or Unbestimmtheit (undeterminedness), whereas his mentor and collaborator Niels Bohr often used Unsicherheit (unsureness). Today in German the most commonly used term for the principle is Unschärfe (blurredness or fuzziness). 
- (physics, quantum mechanics) The principle that there is an absolute limit on the combined accuracy of certain pairs of simultaneous, related measurements, especially that of the position and momentum of a particle. Originally posited as a problem of measurement, it was soon refined as an inherent property of the universe.
- ^ Postscript to Michael Frayn's Copenhagen (New York : Anchor Books, 2000).