The theory which deals with analyses of all consequences of connectivities inherent in molecular structure and chemical transformations. The theory does not produce numerical data but uses available data and searches for regularities that can be attributed to combinatorial and topological origins.
Source:
PAC, 1999, 71, 1919. 'Glossary of terms used in theoretical organic chemistry' on page 1951 (https://doi.org/10.1351/pac199971101919)