realization of the definition of a given quantity, with stated quantity value and associated measurement uncertainty, used as a reference

EXAMPLE 1: 1 kg mass measurement standard with an associated standard measurement uncertainty of 3 μg.
EXAMPLE 2: 100 ohm measurement standard resistor with an associated standard measurement uncertainty of 1 μohm.
EXAMPLE 3: Caesium frequency standard with a relative standard measurement uncertainty of 2  10–15.
EXAMPLE 4: Standard buffer solution with a pH of 7.072 with an associated standard measurement uncertainty of 0.006.
EXAMPLE 5: Set of reference solutions of cortisol in human serum having a certified quantity value with
measurement uncertainty for each solution.
EXAMPLE 6: Reference material providing quantity values with measurement uncertainties for the mass
concentration of each of ten different proteins.