The measurand is defined as a physical quantity to be measured (such as length, weight, and angle). The specification of a measurand requires:
- the knowledge of the species of physical quantity;
- the description of the state of the phenomenon, of the body or of the substance of which the physical quantity constitutes a property (including all the relevant components);
- the chemical entities involved.
It is essential to underline that the term “measurand” does not refer to the object or phenomenon on which a measurement is being performed, but to a specific physical quantity that characterizes them. For example, when we detect the temperature of a liquid, the measurand is not the liquid, but its temperature.