The measurements showing the ideal or 'perfect' sizes of parts on drawings are called

• A. Dimensions
• B. Tolerances
• C. Scale
• D. Prototypes

Answer: (A)

Dimensions are the measurements that specify the exact sizes of features on a drawing—the intended, nominal sizes for length, width, diameter, radius, and so on. They convey the precise numerical values a part should have when finished, guiding manufacturing and inspection. Tolerances, by contrast, define how much those dimensions may vary and still be acceptable, so they address allowable deviation from the ideal size. Scale refers to how large the drawing is relative to the real part, not the actual sizes themselves. Prototypes are physical models used for testing or demonstration, not the measurement standards shown on a drawing.