Thermodynamic temperature is the absolute measure of temperature and is one of the principal parameters of thermodynamics.

Thermodynamic temperature is defined by the third law of thermodynamics in which the theoretically lowest temperature is the null or zero point. At this point, absolute zero, the particle constituents of matter have minimal motion and can become no colder. Thermodynamic temperature is often also called absolute temperature because it does not depend on the properties of a particular material and refers to an absolute zero according to the properties of the ideal gas.

The International System of Units specifies a particular scale for thermodynamic temperature. It uses the kelvin scale for measurement and selects the triple point of water at 273.16 K as the fundamental fixing point

Symbol
$\theta_{\mathrm{abs}}$
Unit
K
Used in
$T_{\mathrm{gas}}$
$\theta_{\mathrm{gas}}$
$\theta_{\mathrm{surf}}$