There are currently two units of temperature in the International System:

Kelvin, symbol K

Degree on the thermodynamic scale of absolute temperatures where the triple point of water is 273.16 K

Degree Celsius, symbol °C

The Celsius temperature t corresponding to the thermodynamic temperature T is defined by the equation t = T – T0 where T0 = 273.15 K

A temperature interval or difference can also be expressed in degrees Celsius. In the past, a number of temperature measurement scales have been defined based on two or more fixed points.

It should be noted that the kelvin is not used with the word degree or the symbol; we say “a kelvin” and not a degree kelvin.