interatomic distances and angles between the bonds(vectors to neighbours) .Then, in the absence of external forces, the generalform becomes

In the three-body term theinteratomic distance is not neededsince the three terms are sufficient to give the relative positions of three atoms in three-dimensional space. Any terms of order higher than2 are also called many-body potentials.In some interatomic potentials the many-body interactions are embedded into the terms of a pair potential (see discussion onEAM-like and bond order