Assertion: polyhedron's edge | /r/HasAspect | opposite directions
Facets:
value: in the two faces
type: LOCATION
Source sentences:
text: If in a polyhedron it is possible to orient the faces so that each edge has opposite directions in the two faces which are adjacent along this edge, then the polyhedron is called orientable, otherwise it is called non-orientable (cf. also Orientation).