What is Temperature Difference?
Temperature difference, as opposed to absolute temperature, is a measure of the relative amounts of internal energy within two bodies. In simple terms, temperature is the measure of the hotness or the coldness of an object. Something that feels hotter generally has a higher temperature and vice versa. Thermodynamics, the branch of physics which deals with the conversion of different forms of energy is dependent on a principal factor which is temperature. There is a series of thermodynamic laws defined based on the movement of heat or the heat flow between objects. Two objects are said to have the same temperature if no heat flows between them. Otherwise heat flows from the hotter to the colder body at a rate determined by the temperature difference.
The SI unit of temperature difference is Celsius (named after Swedish astronomer Anders Celsius), and also known by the older name of degrees Centigrade. Thermodynamics uses the Kelvin scale of measurement which for the measurement of tempertature difference is the same unit. The older Fahrenheit scale is also widely used.
It is necessary to know whether we are dealing with absolute temperatures or temperature differences when converting between different temperature units. The temperature difference measured in Celsius or Fahrenheit does not involve an offset, only a scaling factor.