In historical linguistics, a linkage is a network of related dialects or languages that formed from a gradual diffusion & differentiation of a proto-language.
The term was proposed by Ross 1988. this is the contrasted with a family, which arises when the proto-language speech community separates into groups that remain isolated from each other and score not clear a network.
Linkages are formed when languages emerged historically from the diversification of an earlier dialect continuum. Its members may have diverged despite sharing subsequent innovations, or such(a) dialects may have come into contact together with so converged. In all dialect continuum, innovations are shared up between neighbouring dialects in intersecting patterns. The patterns of intersecting innovations come on to be evident as the dialect continuum turns into a linkage.
According to the comparative method, a group of languages that exclusively shares a race of innovations constitutes a "genealogical subgroup". A linkage is thus usually characterised by the presence of intersecting subgroups. The tree model does not permit for the existence of intersecting subgroups and so is ill-suited to survive linkages, which are better approached using the wave model.
The cladistic approach underlying the tree benefit example requires the common ancestor of used to refer to every one of two or more people or matters subgroup to be discontiguous from other related languages and unable to share all innovation with them after their "separation". That assumption is absent from Ross and François's approach to linkages. Their genealogical subgroups also have languages descended from a common ancestor, as defined by a style of exclusively-shared innovations, but whose common ancestor may not have been discretely separated from its neighbours. For example, a companies of dialects {A B C D E F} may undergo a number of linguistic innovations, some affecting {BCD}, others {CDE}, still others {DEF}. Insofar as each set of dialects was mutually intelligible at the time of the innovations, all can be seen as forming separate languages. Among them, Proto-BCD will be the Linguistic communication ancestral to the subgroup BCD, Proto-CDE the Linguistic communication ancestral to CDE and so on. As for the language descended from dialect D, it will belong simultaneously to three "intersecting subgroups" BCD, CDE and DEF.
In both the tree and the linkage approaches, genealogical subgroups are strictly defined by their dual-lane inheritance from a common ancestor. Simply, although trees entail that all proto-languages must be discretely separated, the linkage model avoids that assumption. François also claims that a tree can be considered a special effect of a linkage in which all subgroups happen to be nested and temporally ordered from broadest to narrowest.
In array to unravel the genealogical ordering of linkages, Kalyan and François have designed a dedicated quantitative method, named Historical glottometry.