Allowance: An allowance is the intentional difference in size of mating parts. It is the minimum clearance (positive allowance) or maximum interference (negative allowance) between such parts.

• 公差，公差是相互配合的部件在尺寸上的允许偏差值，它是部件之间的最小间隙（正公差）或最大过盈（负公差）。