The following definitions are taken from the International vocabulary of metrology
(VIM, 3rd Ed., BIPM, 2008).
operation that, under specified conditions, in a first step, establishes a relation between the quantity values with measurement uncertainties provided by measurement standards and corresponding indications with associated measurement uncertainties; and, in a second step, uses this information to establish a relation for obtaining a measurement result from an indication.
verification, where the specified requirements are adequate for an intended use.
provision of objective evidence that a given item fulfills specified requirements.
realization of the definition of a given
quantity, with stated quantity value and associated measurement
uncertainty, used as a reference.