isogloss

1. (linguistics) A line on a map indicating the geographical boundaries of a linguistic feature.Examples: "Bloch thinks (and we agree with him) that details of isogloss will probably not bear out this kind of grouping."; "The convergence of multiple isoglosses on a map, a "bundle", indicates a boundary between one regional dialect and another."Synonyms: heterogloss

2. (linguistics) A linguistic feature shared between languages or language varieties, through any of various mechanisms, whether genetic inheritance or other linguistic forces.Examples: "There was also a tendency to treat transitive verbs passively, as in Hurrian and Urarṭian; it must, however, be emphasized that this phenomenon may also be considered as an isogloss rather than as an indication of genetic relationship."; "It is likely that the Sardinian forms are related to Lat. afrissa 'dragon lily'. The question regarding its etymology is all but resolved however. It is not quite clear where Pseudo-Apuleius' herbarium [the only known use of afrissa] was composed. If it is North African, as has been proposed, this might be yet another instance of a Sardinian-African Romance isogloss, possibly due to Punic influence."