Design Nomenclature / Form & Geometry
Edge
Also called boundary edge, open edge, border edge, segment
This entry has not been translated yet and is shown in English.
The straight segment between two vertices, and the unit that carries a mesh's structure. How many faces share an edge classifies it: exactly two is manifold interior, one is a boundary edge, three or more is non-manifold. An edge holds no position of its own — moving a vertex moves every edge on it.
In practice
'Open edge' or 'border' for the one-face case; it is what a slicer reports as a hole, and what a border-select finds. Hard and soft edges are a shading attribute, not a structural one.