What is a modifier?

• A. A device to modify color
• B. A description of the allowable variation between a feature and its basic dimensions
• C. A calibration chart
• D. A color code

Answer: (B)

A modifier describes how much a feature may vary from its basic dimensions. On engineering drawings, basic dimensions indicate the exact target size or location, and the tolerance—often conveyed as the modifier—tells you the allowable deviation from that target. For example, if a hole has a basic diameter of 10.00 mm and a tolerance of ±0.05 mm, the actual hole size can range from 9.95 to 10.05 mm. The other options don’t fit because they describe color modification, measurement calibration, or color coding, none of which define how much a feature can vary from its intended dimension.