ENERGETICS may be defined as the science of energy. In systems whose state is changing so slowly that the reactions arising from changing motions can be neglected, whether these systems are in a stationary condition or in a state of steady motion, the energy depends upon the configuration alone, and its mathematical expression can be determined from measure ment of the work required for a sufficient number of single trans formations. Once it is found, all statical relations of the system are implicitly determined along with it, and results of all other transformations can be predicted. The general development of such relations are conveniently classed as a separate branch of physics under the name Energetics first proposed by J. M. Rankine. (See THERMODYNAMICS.)