<unk>  is the<unk>  that is stored.<unk>  exists when there is a force that tends to pull an object back towards some original position when the object is displaced. This force is often called a restoring force. The phrase<unk> ' was coined by William Rankine. For example, when a spring is stretched to the left, it exerts a force to the right so as to return to its original, un-stretched position. Or, suppose that a weight is lifted straight up. The force of gravity will try to bring it back down to its original position. The initial steps of stretching the spring and lifting the weight both require<unk>  to<unk> rform. According to the principle of conservation of<unk> ,<unk>  cannot be created or destroyed; hence this<unk>  cannot disappear. Instead it is stored as<unk> . If the spring is released or the weight is dropped, this stored<unk>  will be converted into kinetic<unk>  by the restoring force — elasticity in the case of the spring, and gravity in the case of the weight.
The more formal definition is that<unk>  is the<unk>  of position, that is, the<unk>  an object is considered to have due to its position in space. There are a number of different types of<unk> , each associated with a particular type of force. More specifically, every conservative force gives rise to<unk> . For example, the work of elastic force is called elastic<unk> ; work of gravitational force is called gravitational<unk> , work of the Coulomb force is called electric<unk> ; work of strong nuclear force or weak nuclear force acting on the baryon charge is called nuclear<unk> ; work of intermolecular forces is called intermolecular<unk> . Chemical<unk> , such as the<unk>  stored in fossil fuels, is the work of Coulomb force during rearrangement of mutual positions of electrons and nuclei in atoms and molecules. Thermal<unk>  usually has two components: the kinetic<unk>  of random motion of particles and<unk>  of their mutual positions.
As a general rule, the work done by a conservative force F will be
where 
Δ
P
E
{\displaystyle \Delta<unk> }
 is the change in the<unk>  associated with that particular force. The most common notations for<unk>  are<unk>  and U. It is important to note that electric<unk>  (commonly denoted with a V for voltage) is not the same as electric<unk> .
Potential energy
Free energy
Gibbs free energy
Concentration
Quantum yield
Peptide sequence
Chemical symbol
Theoretical plate