face, surface

SUのデータ構造(Sketch Up Tips)：faceは同一平面上、surfaceはfaceの集合体

face: In solid geometry, a face is a flat (planar) surface that forms part of the boundary of a solid object;^[1] a three-dimensional solid bounded exclusively by flat faces is a polyhedron.(Wikipedia)

surface: In mathematics, a surface is a generalization of a plane which needs not be flat, that is, the curvature is not necessarily zero. (Wikipedia)

端面 (Proz.com)

Is a Curved Surface a Face? (Ask Dr. Math)