 Solution

For solid modelling, a polyhedron is a solid whose boundary consists of finitely many planar polygons, called faces, meeting along straight edges and at vertices of a polyhedron. A face is not merely a list of arbitrary spatial points: its boundary must lie in one plane and bound a valid planar region. The boundary is closed and consistently oriented so that inside and outside are defined.

For example, a tetrahedron has four triangular faces, six edges and four vertices of a polyhedron. A more general polyhedron need not be convex and can have handles or cavities. The concise definition is