https://doi.org/10.1351/goldbook.U06554
Non-SI unit of mass (equal to the @A00497@), defined as one twelfth of the mass of a carbon-12 atom in its @G02704@ and used to express masses of atomic particles, \(\text{u}\approx 1.660\ 5402(10)\times 10^{-27}\ \text{kg}\).