In historical linguistics, a linkage is a network of related dialects or languages that formed from a gradual diffusion and differentiation of a proto-language.
It is contrasted with a family, which arises when the proto-language speech community separates into groups that remain isolated from each other and do not form a network.
[4][5][6] The cladistic approach underlying the tree model requires the common ancestor of each subgroup to be discontiguous from other related languages and unable to share any innovation with them after their "separation".
François also claims that a tree can be considered a special case of a linkage in which all subgroups happen to be nested and temporally ordered from broadest to narrowest.
[3] In order to unravel the genealogical structure of linkages, Kalyan and François have designed a dedicated quantitative method, named Historical glottometry.
He cites the Oceanic languages of northern Vanuatu as well as those of Fiji and of Polynesia and at least some sections of the Pama-Nyungan, Athabaskan, Semitic, Sinitic, and Indo-European families.