15031 IUPAC Gold Book - Shannon–Wiener diversity index 10.1351/goldbook.15031 15031 current 1 Index based on the assumption that all species are represented in the sample studied and that the sample was obtained randomly, giving the following mathematical relationship: \[H = -\sum \limits_{i=1}^S p_{i} \log p_{i}\] where \(p_{i}\) is the fraction of individuals belonging to the \(i\)-th species and \(S\) is the number of species. The Shannon index is affected by both the number of species and their equitability, or evenness. Both a greater number of species and a more even distribution increase diversity as measured by \(H\). The most important source of error in this index is failure of sampling to include all species from the community of interest. community https://goldbook.iupac.org//terms/view/14531 diversity index https://goldbook.iupac.org//terms/view/14599 PAC, 2009, 81, 829. 'Glossary of terms used in ecotoxicology (IUPAC Recommendations 2009)' on page 944 (https://doi.org/10.1351/PAC-REC-08-07-09) https://goldbook.iupac.org/terms/view/15031/html https://goldbook.iupac.org/terms/view/15031/json https://goldbook.iupac.org/terms/view/15031/plain Citation: 'Shannon–Wiener diversity index' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351/goldbook.15031 The IUPAC Gold Book is licensed under Creative Commons Attribution-ShareAlike CC BY-SA 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) for individual terms. If you are interested in licensing the Gold Book for commercial use, please contact the IUPAC Executive Director at executivedirector@iupac.org . The International Union of Pure and Applied Chemistry (IUPAC) is continuously reviewing and, where needed, updating terms in the Compendium of Chemical Terminology (the IUPAC Gold Book). Users of these terms are encouraged to include the version of a term with its use and to check regularly for updates to term definitions that you are using. 2026-04-18T17:55:19+00:00