temperature

Temperature (also thermodynamic temperature in the SI system) is a state variable describing the average kinetic energy of particles. The zeroth law of thermodynamics describes temperature as a quantity that has the same value at every point of an isolated system in equilibrium.

Temperature is a macroscopic quantity, so it makes no sense to talk about temperature at the atomic and subatomic level.

• Marking
  For data in kelvin, the symbol is T. For data in degrees Celsius, the symbols t or ϑ are also possible (but t is confused with the symbol for time).

  Units
  The SI unit of temperature is Kelvin. However, in everyday life, for practical reasons, degrees Celsius or degrees Fahrenheit are more often used.

  Temperature measuring
  We distinguish between two methods of temperature measurement:

  Directly
  thermometer
  gas thermometer
  liquid thermometer
  bimetallic thermometer
  thermocouple
  a thermistor (a resistor whose resistivity changes due to temperature)
  Indirectly
  pyrometer
  thermograph