kilogram

https://doi.org/10.1351/goldbook.K03391
SI base unit for mass (symbol: \(\text{kg}\)). The kilogram is equal to the mass of the international prototype of the kilogram.
Sources:
Green Book, 2nd ed., p. 70 [Terms] [Book]
PAC, 1996, 68, 957. (Glossary of terms in quantities and units in Clinical Chemistry (IUPAC-IFCC Recommendations 1996)) on page 978 [Terms] [Paper]