A thermodynamic potential is a scalar quantity used to represent the thermodynamic state of a system. Similarly to the potential energy of the conservative gravitational field, defined as capacity to do work, various thermodynamic potentials have similar meanings. The author of the term of thermodynamic potentials is Pierre Duhem in an 1886 work. Josiah Willard Gibbs in his papers used the term fundamental functions. Effects of changes in thermodynamic potentials can sometimes be measured directly, while their absolute magnitudes can only be assessed using computational chemistry or similar methods.