Vertex arrangement
In geometry, a vertex arrangement is a set of points in space described by their relative positions. They can be described by their use in polytopes. For example, a "square vertex arrangement" is understood to mean four points in a plane, equal distance and angles from a center point. Two polytopes share the same "vertex arrangement" if they share the same 0-skeleton. A group of polytopes that shares a vertex arrangement is called an "army". Vertex arrangement. The same set of vertices can be connected by edges in different ways. For example, the "pentagon" and "pentagram" have  the same "vertex arrangement", while the second connects alternate vertices. A "vertex arrangement" is often described by the convex hull polytope which contains it. For example, the regular "pentagram" can be said to have a (regular) "pentagonal vertex arrangement". Infinite tilings can also share common "vertex arrangements". For example, this triangular lattice of points can be connected to form either isosceles triangles or rhombic faces. Edge arrangement. Polyhedra can also share an "edge arrangement" while differing in their faces. For example, the self-intersecting "great dodecahedron" shares its edge arrangement with the convex "icosahedron": A group polytopes that share both  a "vertex arrangement" and an "edge arrangement" are called a "regiment". Face arrangement. 4-polytopes can also have the same "face arrangement" which means they have similar vertex, edge, and face arrangements, but may differ in their cells. For example, of the ten nonconvex regular Schläfli-Hess polychora, there are only 7 unique face arrangements. For example, the grand stellated 120-cell and great stellated 120-cell, both with pentagrammic faces, appear visually indistinguishable without a representation of their cells: Classes of similar polytopes. George Olshevsky advocates the term "regiment" for a set of polytopes that share an edge arrangement , and more generally "n-regiment" for a set of polytopes that share elements up to dimension "n". Synonyms for special cases include "company" for a 2-regiment (sharing faces) and "army" for a 0-regiment (sharing vertices).