Surface roughness is the measure of the microscopic irregularities or variations in a part's surface after manufacturing processes such as machining, grinding, or polishing. It is typically quantified by parameters like Ra (average roughness) or Rz (average maximum height of the surface profile). Controlling surface roughness is crucial in ensuring parts meet functional specifications, such as reducing friction, preventing wear, or ensuring a proper seal. For example, smoother surfaces are often required for components like bearings or seals to ensure efficient operation and longevity. By specifying acceptable surface roughness in design, manufacturers can optimize performance, reduce assembly errors, and enhance product durability.