Phenetics (numerical taxonomy) classifies organisms based on overall similarity of observable (phenotypic) characters — morphological, physiological, behavioural, biochemical — without regard to evolutionary history or phylogeny. Developed by Sokal and Sneath, it uses multivariate statistical analyses (cluster analysis, phenograms) to group organisms by similarity scores. It contrasts with cladistics (based on shared derived characters/synapomorphies) and phylogenetics (based on evolutionary relationships).