What do you call a geographic boundary that marks a difference in a particular linguistic feature?

An isogloss is a geographic boundary that differentiates areas based on the presence or absence of specific linguistic features. These features can include variations in vocabulary, pronunciation, or grammatical constructions. For example, an isogloss might separate regions where a particular term for a common object is used versus regions that use another term.

Understanding the concept of isogloss helps in the study of sociolinguistics and dialectology because it illustrates how language can vary geographically, often aligned with social, cultural, or historical divisions within a population. This term specifically focuses on linguistic characteristics, making it distinct from the other options listed.

Political borders, for instance, are defined by legal or governmental lines that often do not correspond to cultural or linguistic differences. Diaspora refers to the dispersion of people from their original homeland and does not inherently relate to linguistic boundaries. While dialects pertain to variations of language within a broader language group, they do not represent the geographic boundaries or lines that define where these variations occur, as an isogloss does.