Class refers to the system of atoms for which atomconnectivity permutations are applied; family is characterised by a combination of total connections and the set of general atomconnectivity configuration patterns; genus captures more nuanced details of the atom-connectivity configuration patterns; species represents a specific arrangement of atom connections for the set of atoms. The distinctions between family and genus are demonstrated herein through the worked examples and is based upon the mathematics notions of set partitioning, Bell numbers, and equivalence relations.