Primary form is used in surface metrology

Surface metrology

Surface metrology is the measurement of small-scale features on surfaces, and is a branch of metrology. Surface primary form, surface waviness and surface roughness are the parameters most commonly associated with the field...

 to refer to the over-all shape of a surface which can be measured quantitatively, as contrasted with more local or higher-spatial frequency variations in the surface dimensions such as surface waviness or surface roughness or surface finish

Surface finish

Surface finish, also known as surface texture, is the characteristics of a surface. It has three components: lay, surface roughness, and waviness.-Lay:...

. Examples of primary form include surface flatness, surface roundness, and surface cylindricity. Each of these classes of primary form can be quantitatively defined in several different ways depending upon the intended purpose of the surface, such a statistical least squares flatness, and overall flatness (aka max-min flatness).