N-sphere

An $n-$sphere is a finite-dimensional arcwise-connected topological space.
An $n-$sphere is a space that is homeomorphic to the $n-$dimensional sphere $S^n$ in $\mathbb{R}^{n+1}$, where $$S^n = \left \{ x \in \mathbb{R}^{n+1} : ||x|| = 1 \right \}, \quad \text{each } n = 1,2,...$$ An $n-$sphere is a continuum. A $1-$sphere is called a simple closed curve.[1]