Electron-volts
An electron-volt (eV) is used in the fields of atomic and particle physics. It is the amount of energy gained or lost by a single electron when it is accelerated through an electric potential difference of one volt.
Btu (thermoc.)
The Btu (thermochemical) variant aligns with the thermochemical calorie and is defined as the amount of energy required to raise the temperature of one pound of water by one degree Fahrenheit at a constant pressure of one atmosphere and is equivalent to approximately 1,054.350 Joules.