Abstract
Measurement ‐ a central epistemic activity in science ‐ relates a number and a quantity in an effort to estimate the magnitude of that quantity. A quantity is typically a property of a physical configuration, such as length or weight, and determines a function that applies to a domain or class of objects. At this high level of abstraction, the description of the purpose and relation of measurement is metaphysically neutral, leaving open the question of whether the domain is observable (empirical) or unobservable (nonempirical).