Isoglossa

An isoglossa (plural: isoglosses) is a geographic boundary line on a linguistic map marking the limit of a particular linguistic feature, such as the pronunciation of a word, the use of a specific word, or the occurrence of a certain grammatical construction. It represents the spatial extent of that feature.

Isoglosses are used in dialectology to analyze the distribution of language variations across geographic areas. They can bundle together to form isogloss bundles, which indicate a more significant dialect boundary. While individual isoglosses may cross or overlap, a large concentration of isoglosses in a relatively narrow area suggests a major dialectal division.

The study of isoglosses helps linguists understand language change, language contact, and the history of language development. Mapping these boundaries allows for the visualization of regional linguistic variation and the identification of distinct dialect regions. Isoglosses are not impermeable barriers, and linguistic features can spread across them over time, leading to language change and convergence. The complexity of isogloss patterns often reflects the interplay of geographical, social, and historical factors.