04439 IUPAC Gold Book - partition function 10.1351/goldbook.P04439 P04439 current 1 For a molecule the ratio of the total number of molecules to their number in the non-degenerate ground state. ground state https://goldbook.iupac.org//terms/view/G02704 Green Book, 2nd ed., p. 39 (https://goldbook.iupac.org/files/pdf/green_book_2ed.pdf) https://goldbook.iupac.org/terms/view/P04439/html https://goldbook.iupac.org/terms/view/P04439/json https://goldbook.iupac.org/terms/view/P04439/plain Citation: 'partition function' 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.P04439 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. 2026-05-30T21:53:04+00:00