kelvin

https://dx.doi.org/10.1351/goldbook.K03374
SI base unit of thermodynamic temperature (symbol: K). The kelvin is the fraction 1/273.16 of the thermodynamic temperature of the triple point of water.
Source:
PAC, 1996, 68, 957 (Glossary of terms in quantities and units in Clinical Chemistry (IUPAC-IFCC Recommendations 1996)) on page 977