Binding energy

In physics, binding energy (also called separation energy) is the minimum energy required to disassemble a system of particles into separate parts. This energy is equal to the mass defect minus the amount of energy, or mass, that is released when a bound system (which typically has a lower potential energy than the sum of its constituent parts) is created, and is what keeps the system together. In general, binding energy represents the mechanical work that must be done against the forces that hold an object together, disassembling the object into its component parts with enough distance between them so that further separation requires negligible additional work. In bound systems, if the binding energy is removed from the system, it must be subtracted from the mass of the unbound system, because this energy has mass. Thus, if energy is removed (or emitted) from the system at the time it is bound, this loss of energy will also result in the loss of the system's mass. The mass of the system is not conserved in this process because the system is 'open' (i.e., is not an isolated system to mass or energy input or loss) during the binding process.