If by “metroloy” you mean “metrology,” it refers to the science of measurement, including the measurement of mechanical parts. Metrology plays a crucial role in ensuring that mechanical parts meet the required specifications and are manufactured to a high level of accuracy.
There are various methods and tools used in metrology to measure the dimensions, surface characteristics, and other properties of mechanical parts.
These include coordinate measuring machines (CMMs), optical measurement systems, surface profilometers, and various types of gauges and calipers

Metrology is critical for ensuring the quality and performance of mechanical parts, as well as for ensuring that they are compatible with other parts in an assembly. The accuracy of metrology measurements can have a significant impact on the performance, safety, and reliability of mechanical systems.