Natural units are convenient for abstract theoretical considerations, because they help keep the equations clean. For practical applications, though, other systems of units are normally used. Two of the most commonly used systems are International System of units (SI) and Gaussian units. Gaussian units can be regarded as a compromise between natural units and SI units, but Gaussian units introduce a new artifact that is absent in both of the other systems. Heaviside-Lorentz units is a compromise similar to Gaussian units, but without the artifact. This article introduces these systems, with special emphasis on the International System.
