For questions about the science of measurement, such as how units are defined or how practical measurements are connected to those definitions.
The International Bureau of Weight and Measures defines Metrology as " the science of measurement and its application. Metrology includes all theoretical and practical aspects of measurement, whatever the measurement uncertainty and field of application." This includes the definition of measurement units and how practical measurements can be connected to those definitions. Metrology provides the basis for the measurements that are essential in science, technology, engineering, medicine, commerce, industry, and everyday life.