A general result in terms of ‘work’ of two states of the body is derived to prove energy-related theorems. The energy balance equation and the uniqueness theoremsUniqueness theorems for linear elastic solutions are derived. Betti’sBetti’s reciprocal theorem and Maxwell’s reciprocal theoremsMaxwell’s reciprocal theorem, the principles of stationary potential energy and complementary potential energyPrinciple of potential energy, Castigliano’s two theorems and Hamilton’s principleHamilton’s principle are presented.