N-sphere
In mathematics, an n-sphere or hypersphere is an n {\displaystyle n} -dimensional generalization of the 1 {\displaystyle 1} -dimensional circle and 2 {\displaystyle 2} -dimensional sphere to any non-negative integer n {\displaystyle n} . The circle is considered 1-dimensional and the sphere 2-dimensional because a point within them has one and two degrees of freedom respectively.