# ISO 31-4: Wikis

Note: Many of our articles have direct quotes from sources you can cite, within the Wikipedia article! This article doesn't yet, but we're working on it! See more info or our list of citable articles.

# Encyclopedia

Updated live from Wikipedia, last check: May 22, 2013 17:48 UTC (52 seconds ago)

ISO 31-4 is the part of international standard ISO 31 that defines names and symbols for quantities and units related to heat.

Its definitions include:

Quantity Unit Remarks
Name Symbol Name Symbol Definition
thermodynamic temperature T, (Θ) kelvin K The kelvin is the fraction 1/273.16 of the thermodynamic temperature of the triple point of water. For practical measurements, the International Temperature Scale of 1990 defines several fixed points and interpolation procedures.
Celsius temperature t, φ degree Celsius °C The degree Celsius is a special name for the unit kelvin, for use in stating values of Celsius temperature. t = TT0, where T0 = 273.15 K
linear expansion coefficient αl reciprocal kelvin, kelvin to the power negative 1 K−1 $\alpha_l=\frac 1l\frac lT$
...

Annex A of ISO 31-4 lists units of heat based on the foot, pound and second and some other units, including the degree Rankine, degree Fahrenheit, British thermal unit and others. Annex B lists conversion factors for three versions of the calorie.