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 (3.9°C)
The Btu (3.9°C) is defined as the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit at the temperature where water reaches its maximum density which occurs at approximately 3.9°C (39°F).