Index
0-skeleton
1-skeleton
2-skeleton
3-skeleton

This shows the skeleta of the simplex $\Delta_3$. The full simplex is the set of points $(x_0,x_1,x_2,x_3)\in\mathbb{R}^4$ where $x_0,x_1,x_2,x_3\geq 0$ and $x_0+x_1+x_2+x_3=1$. The $k$-skeleton is the subspace where at least $3-k$ of the coordinates $x_i$ are zero.

The $3$-skeleton consists of the full solid tetrahedron.