Celsius temperature, t, θ

https://dx.doi.org/10.1351/goldbook.C00928
Thermodynamic temperature minus 273.15 K, invariably expressed in the SI unit degree Celsius(°C) which is equal to the kelvin. Sometimes the misnomer centigrade temperature is used for Celsius temperature.
Source:
PAC, 1996, 68, 957 (Glossary of terms in quantities and units in Clinical Chemistry (IUPAC-IFCC Recommendations 1996)) on page 965