Different atom-connection configurations arise by only permutating connectivity between the bonders and the sites. All other parts of the molecular system are called "spectator" atoms and are, within this methodology, characterised by their atom connections remaining fixed throughout. With m bonding sites 𝒮 and n bonders ℬ, this partitioning approach is termed the 𝒮 𝑚 ℬ 𝑛 class.