isoglosses

Noun

isogloss (plural isoglosses)

1. A line on a map indicating the geographical boundaries of a linguistic feature.
   • Bloch thinks (and we agree with him) that details of isogloss will probably not bear out this kind of grouping.1921, The Calcutta Review, Calcutta: University of Calcutta, →OCLC, page 285

   Synonyms:

   heterogloss

2. A linguistic feature shared between languages or language varieties, through any of various mechanisms, whether genetic inheritance or other linguistic forces.
   • 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.1970, W[illiam] F[oxwell] Albright, T[homas] O[den] Lambdin, “The Evidence of Language”, in I[orwerth] E[iddon] S[tephen] Edwards, C[yril] J[ohn] Gadd, N[icholas] G[eoffrey] L[emprière] Hammond...