Absolute Temperature Definition

macro photo of thermometer at body temperature

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Absolute temperature is temperature measured using the Kelvin scale where zero is absolute zero. The zero point is the temperature at which particles of matter have their minimum motion and can become no colder (minimum energy). Because it is "absolute," a thermodynamic temperature reading is not followed by a degree symbol.

Although the Celsius scale is based on the Kelvin scale, it does not measure absolute temperature because its units are not relative to absolute zero. The Rankine scale, which has a degree interval the same as the Fahrenheit scale, is another absolute temperature scale. Like Celsius, Fahrenheit is not an absolute scale.