Shannon entropy (information entropy), being the expected value of the information of an event, is a quantity of the same type and with the same units as information. The International System of Units, by assigning the same units (joule per kelvin) both to heat capacity and to thermodynamic entropy implicitly treats information entropy as a quantity of dimension one, with 1 nat = 1.[lower-alpha 1] Physical systems of natural units that normalize the Boltzmann constant to 1 are effectively measuring thermodynamic entropy in nats.