## ::Temperature

### ::concepts

Energy::scale    Which::system    Absolute::point    ''T''::state    Kelvin::between    Kinetic::defined

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Note: Conjugate variables in italics
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Specific heat capacity  $c=$
 $T$ $\partial S$ $N$ $\partial T$
Compressibility  $\beta=-$
 $1$ $\partial V$ $V$ $\partial p$
Thermal expansion  $\alpha=$
 $1$ $\partial V$ $V$ $\partial T$

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Body temperature variation
Annual mean temperature around the world

A temperature is an objective comparative measure of hot or cold. It is measured by a thermometer, which may work through the bulk behavior of a thermometric material, detection of thermal radiation, or particle kinetic energy. Several scales and units exist for measuring temperature, the most common being Celsius (denoted °C; formerly called centigrade), Fahrenheit (denoted °F), and, especially in science, Kelvin (denoted K).

The coldest theoretical temperature is absolute zero, at which the thermal motion in matter would be zero. However, an actual physical system or object can never attain a temperature of absolute zero. Absolute zero is denoted as 0 K on the Kelvin scale, −273.15 °C on the Celsius scale, and −459.67 °F on the Fahrenheit scale.

The kinetic theory offers a valuable but limited account of the behavior of the materials of macroscopic systems, especially of fluids. It indicates the absolute temperature as proportional to the average kinetic energy of the random microscopic motions of their constituent microscopic particles such as electrons, atoms, and molecules.

Thermal vibration of a segment of protein alpha helix: The amplitude of the vibrations increases with temperature.

Temperature is important in all fields of natural science, including physics, geology, chemistry, atmospheric sciences, medicine, and biology—as well as most aspects of daily life.

Temperature sections
Intro  Effects of temperature  Temperature scales  Thermodynamic approach to temperature  Kinetic theory approach to temperature  Basic theory  Heat capacity  Temperature measurement  Theoretical foundation  Examples of temperature  See also  Notes and references  Further reading  External links

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