which is the us english term for thermal energy
Thermal energy Thermal energy is a term used loosely as a synonym for more rigorously-defined thermodynamic quantities such as the internal energy of a system; heat or sensible heat, which are defined as types of transfer of energy (as is work); or for the characteristic energy of a degree of freedom in a thermal system   k T  {\displaystyle kT} , where   T  {\displaystyle T}  is temperature and   k  {\displaystyle k}  is the Boltzmann constant.
Calorie Although these units relate to the metric system, all of them have been considered obsolete in science since the adoption of the SI system.[3] The unit of energy in the International System of Units is the joule. One small calorie is approximately 4.2 joules (so one large calorie is about 4.2 kilojoules). The factor used to convert calories to joules at a given temperature is numerically equivalent to the specific heat capacity of water expressed in joules per kelvin per gram (or per kilogram, for kilocalories). The precise conversion factor depends on the definition adopted.