14.2.2—The scale of thermodynamic temperature does not depend on the property of

The thermodynamic temperature scale is based on universal physical principles rather than a chosen material property; the kelvin is the SI unit.

A practical thermometer is calibrated to approximate this scale, but its raw property may be nonlinear or limited in range.

A gas, resistance and radiation thermometer can agree after calibration even though their measured properties differ.

The Celsius scale and a material’s expansion are convenient representations, not the fundamental definition of temperature.