Surface roughness often shortened to roughness, is a component of surface texture. It is quantified by the deviations in the direction of the normal vector of a real surface from its ideal form. If these deviations are large, the surface is rough; if they are small, the surface is smooth.
Surface Roughness Testing measures the condition of the surface of a machined part. This can affect how well the parts fit together or slide on one another. Roughness can be measure using a profilometer and is usually measured in RMS (root mean square) or RA (roughness average).