Engineering tolerance is the permissible limit or limits of variation in:

Dimensions, properties, or conditions may have some variation without significantly affecting functioning of systems, machines, structures, etc. 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. If the tolerance is too restrictive, the machine being incapable of functioning in most environments, it is said to be intolerant.