Celsius temperature, \(t\), \(\theta\)

https://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.
Sources:
Green Book, 2nd ed., p. 48 (https://dev.goldbook.iupac.org/files/pdf/green_book_2ed.pdf)
PAC, 1996, 68, 957. 'Glossary of terms in quantities and units in Clinical Chemistry (IUPAC-IFCC Recommendations 1996)' on page 965 (https://doi.org/10.1351/pac199668040957)