A group of four elements, also called a quadruplet or tetrad.
Quadruple
See also
Amicable Quadruple, Diophantine Set, Monad, Pair, Prime Quadruplet, Pythagorean Quadruple, Tetrad, Triad, Triple, Twins, Vector Quadruple ProductExplore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "Quadruple." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Quadruple.html