HOW TO MEASURE TOLERANCE, LIMIT, FIT, ALLOWANCE IN ENGINEERING
The term fit refers to the relationship between two mating parts of components in order to deliver their specific function. It also refers to how these components are intended to fit together when it comes to their clearances, tolerances, and dimensions.
Tolerance is the amount of random deviation or variation permitted for a given dimension.
Allowance is a planned difference between a nominal or reference value and an exact value.
Clearance is the intentional space between two parts. Interference is the intentional overlap between two parts.