Isogloss

An isogloss is a geographic boundary marking where a particular linguistic feature changes, such as a sound, word, or grammatical form.

Dialectology: The study of regional and social variation in language. Isoglosses are a basic mapping tool in the study of dialects.
Linguistic variable: A language feature that has multiple forms whose distribution can be studied. An isogloss traces where one variable’s forms change across space.
Benrath line: A German dialect boundary separating varieties that pronounce maken and machen differently. This isogloss marks a major division within the history of German dialects.
Isogloss bundle: A cluster of isoglosses that coincide or run close together. A bundle combines multiple boundaries, unlike an isogloss tracing one feature.
Linguistic atlas: A collection of maps showing the geographic distribution of linguistic features. Atlas maps plot feature distributions from which isoglosses are drawn.
Phonological variation: Differences in speech sounds across speakers, styles, or regions. Sound changes are among the most commonly mapped linguistic features.
Uerdingen line: A German dialect boundary separating ik from ich for the first-person singular pronoun. Its contrasting pronouns make a classic, named isogloss easy to identify.
Dialect boundary: A geographic division between areas whose speech varieties differ systematically. An isogloss marks one feature, while a dialect boundary may summarize broader differences.
Dialect continuum: A sequence of neighboring dialects that vary gradually, often without sharp boundaries. Gradual variation can make any single isogloss an incomplete dialect boundary.
Lexical variation: Differences in the words used for the same meaning across speakers or regions. Word choices can divide a map into areas with distinct usage.

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