similarity index

synonym: similarity distance
https://doi.org/10.1351/goldbook.10141

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.
See: city-block distance, Euclidean distance, Mahalanobis distance, Tanimoto similarity index, Ward’s minimum variance method
Source:
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)