Metrology is a science of measurement. Metrology may be divided depending upon the quantity under consideration into: metrology of length, metrology of time etc. Depending upon the field of application it is divided into industrial metrology, medical metrology etc. Engineering metrology is restricted to the measurement of length, angles and other quantities which are expressed in linear or angular terms. For every kind of quantity measured, there must be a unit to measure it. This will enable the quantity to be measured in number of that unit. Further, in order that this unit is followed by all; there must be a universal standard and the various units for various parameters of importance must be standardized. It is also necessary to see whether the result is given with sufficient correctness and accuracy for a particular need or not. This will depend on the method of measurement, measuring devices used etc. Thus, in a broader sense metrology is not limited to length and angle measurement but also concerned with numerous problems theoretical as well as practical related with measurement such as:  Units of measurement and their standards, which is concerned with the establishment, reproduction, conservation and transfer of units of measurement and their standards.  Methods of measurement based on agreed units and standards.  Errors of measurement.  Measuring instruments and devices.  Accuracy of measuring instruments and their care.  Industrial inspection and its various techniques.  Design, manufacturing and testing of gauges of all kinds.