SI REFERENCE POINT
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kelvin

The kelvin, unit of thermodynamic temperature, is the fraction $1/273.16$ of the thermodynamic temperature of the triple point of water.

This definition is valid from 1967-10-13 to 2019-05-19
Unit kelvin
Symbol K
Quantity thermodynamic temperature
Defining Resolution
CGPM Resolution 4 (1967)
Unit Type SI base unit
Notes:
  1. The 13th CGPM (1967, Resolution 3) also decided that the unit kelvin and its symbol $K$ should be used to express an interval or a difference of temperature.
  2. In addition to the thermodynamic temperature (symbol $T$), expressed in kelvins, use is also made of Celsius temperature (symbol $t$) defined by the equation where ${T_{0}}$ = 273,15 K by definition. To express celsius temperature, the unit "degree Celsius" which is equal to the unit "kelvin" is used; in this case, "degree Celsius" is a special name used in place of "kelvin". An interval or difference of Celsius temperature can however, be expressed in kelvin as well as in degrees Celsius.