Engineering Tolerance

Engineering tolerance is the permissible limit or limits of variation in

1. a physical dimension,
2. a measured value or physical property of a material, manufactured object, system, or service,
3. other measured values (such as temperature, humidity, etc.).
4. in engineering and safety, a physical distance or space (tolerance), as in a truck (lorry), train or boat under a bridge as well as a train in a tunnel (see structure gauge and loading gauge).
5. in mechanical engineering the space between a bolt and a nut or a hole, etc..

Dimensions, properties, or conditions may vary within certain practical limits without significantly affecting functioning of equipment or a process. Tolerances are specified to allow reasonable leeway for imperfections and inherent variability without compromising performance.

A variation beyond the tolerance (for example, a temperature that's too hot or too cold) is said to be non-compliant, rejected, or exceeding the tolerance (regardless of if this breach was of the lower or the upper bound). If the tolerance is set too restrictive, resulting in most objects run by it being rejected, it is said to be intolerant.