ISO 31-4 is the part of international standard

International standard

International standards are standards developed by international standards organizations. International standards are available for consideration and use, worldwide...

 ISO 31

ISO 31

International Standard ISO 31 was the most widely respected style guide for the use of physical quantities and units of measurement, and formulas involving them, in scientific and educational documents worldwide...

 that defines names and symbols for quantities

Physical quantity

A physical quantity is a physical property of a phenomenon, body, or substance, that can be quantified by measurement.-Definition of a physical quantity:Formally, the International Vocabulary of Metrology, 3rd edition defines quantity as:...

 and units related to heat.

Its definitions include:

Quantity		Unit			Remarks
Name	Symbol	|Name	Symbol	Definition
thermodynamic temperature Thermodynamic temperature Thermodynamic temperature is the absolute measure of temperature and is one of the principal parameters of thermodynamics. Thermodynamic temperature is an "absolute" scale because it is the measure of the fundamental property underlying temperature: its null or zero point, absolute zero, is the...	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 International Temperature Scale of 1990 The International Temperature Scale of 1990 is an equipment calibration standard for making measurements on the Kelvin and Celsius temperature scales. ITS–90 is an approximation of the thermodynamic temperature scale that facilitates the comparability and compatibility of temperature measurements...  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 = T − T0, where T0 = 273.15 K
linear expansion coefficient	αl	reciprocal kelvin, kelvin to the power negative 1	K−1
...

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

British thermal unit

The British thermal unit is a traditional unit of energy equal to about 1055 joules. It is approximately the amount of energy needed to heat of water, which is exactly one tenth of a UK gallon or about 0.1198 US gallons, from 39°F to 40°F...

 and others. Annex B lists conversion factors for three versions of the calorie

Calorie

The calorie is a pre-SI metric unit of energy. It was first defined by Nicolas Clément in 1824 as a unit of heat, entering French and English dictionaries between 1841 and 1867. In most fields its use is archaic, having been replaced by the SI unit of energy, the joule...

.