Definition & Meaning of "isoglass"

What is an "isoglass"?

An isogloss is a boundary line on a map that shows where certain linguistic features, like pronunciation, vocabulary, or grammar, differ between regions. It marks the point where one way of speaking ends and another begins, often separating different dialects or speech varieties. Isoglosses help linguists understand how language changes across geographic areas and can show the spread of certain linguistic traits within a language or across related languages. These lines often reflect cultural or social influences on language use in different regions.