abstract:In mathematics, the Klein four-group (or just Klein group or Vierergruppe (), often symbolized by the letter V) is the group Z2 × Z2, the direct product of two copies of the cyclic group of order 2. It was named Vierergruppe by Felix Klein in his Vorlesungen über das Ikosaeder und die Auflösung der Gleichungen vom fünften Grade in 1884.