- A smooth surface has no roughness or projections, often as a result of wear, planing, polishing, etc.
- Even is applied to a surface that is uniformly level or flat, or to a surface that is in the same plane with, or in a plane parallel to, another
- Plane describes a real or imaginary surface that is absolutely flat and wholly contains every straight line joining any two points lying in it
- Flat implies the absence to any marked degree of depressions or elevations in a surface, in whatever direction it lies
- Level describes a surface that has no part higher than any other, and is applied to a surface that is parallel to the plane of the horizon or that is the same height as, or in the same plane with, another