Megaelectron-volts
A megaelectron-volt (MeV) is a unit of energy used in particle and nuclear physics. It is derived from the electron-volt (eV) - the amount of kinetic energy gained or lost by an electron when it moves through one volt.
Btu
The British Thermal Unit (Btu) is defined as the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit. It is primarily used in the United States to describe the energy content of fuels and the power of heating and cooling systems.