{"term":{"id":"10141","title":"similarity index","longtitle":"IUPAC Gold Book - similarity index","doi":"10.1351\/goldbook.10141","code":"10141","status":"current","synonym":"<em>synonym<\/em>: similarity distance","definitions":[{"id":1,"text":"Quantity that describes the equivalence of two objects characterised by multivariate data.","notes":{"1":"A similarity index may be in the interval, where 0 is complete dissimilarity and 1 is complete equivalence.","2":"When the term \"distance\" is used the quantity is some function of the differences of coordinates in the multivariate data space."},"links":[{"term":"Euclidean distance","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/10124"},{"term":"Mahalanobis distance","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/10134"},{"term":"Tanimoto similarity index","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/10145"},{"term":"Ward’s minimum variance method","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/10148"},{"term":"city-block distance","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/10120"},{"term":"multivariate data","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/10055"}],"sources":["PAC, 2016, 88, 407. 'Vocabulary of concepts and terms in chemometrics (IUPAC Recommendations 2016)' on page 431 (https:\/\/doi.org\/10.1515\/pac-2015-0605)"]}],"altoutputs":{"html":"https:\/\/goldbook.iupac.org\/terms\/view\/10141\/html","xml":"https:\/\/goldbook.iupac.org\/terms\/view\/10141\/xml","plain":"https:\/\/goldbook.iupac.org\/terms\/view\/10141\/plain"},"citation":"Citation: 'similarity 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.10141","license":"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.","collection":"If you are interested in licensing the Gold Book for commercial use, please contact the IUPAC Executive Director at executivedirector@iupac.org .","disclaimer":"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.","accessed":"2026-08-06T07:43:30+00:00"}}