Lexicostatistics

Lexicostatistics is a quantitative method in historical linguistics that gauges how closely two or more languages are genealogically related by measuring the percentage of cognates they share within a fixed list of basic, culture-neutral vocabulary — classically Morris Swadesh's 100- or 200-word list. By converting word comparisons into similarity percentages, it produces a matrix of pairwise scores from which subgroupings within a language family can be inferred. It is the statistical core that underlies glottochronology, but on its own it makes no claim about absolute dates — it speaks only to degree of relatedness.