The meaning of “quantity” in measurement

Measurement is aimed at assigning a value to “a quantity of a thing”. Therefore a clear statement of what a quantity is appears to be a required condition to interpret unambiguously the results of a measurement. However, the concept of quantity is seldom analyzed in detail in even the foundational works of metrology, and far too often, quantities are “defined” in terms of attributes, characteristics, qualities, etc. while leaving such terms in themselves undefined. The aim of this paper is to discuss the meaning of “quantity” (or, as it will be adopted here for the sake of generality, “attribute”) as it is used in measurement, also drawing several conclusions on the concept of measurement itself