Hosoya index

The Hosoya index, also known as the Hosoya polynomial or the Hosoya number, is a graph-theoretic invariant used to measure the structural complexity of a molecular graph, which represents a chemical compound. Named after Hiroshi Hosoya, the index is particularly useful in the field of cheminformatics and quantitative structure-activity relationship (QSAR) studies. The Hosoya index is defined as the total number of matchings (or perfect matchings) in a graph.