The definition of an isogloss is a line on a map that marks the boundary between areas where language features are different.(noun)
An example of an isogloss is the line on a map that shows the division of two populations which have different pronunciations for a a specific vowel.
See isogloss in Webster's New World College Dictionary
Origin: < iso- + Gr glōssa, tongue, speech: see gloss
See isogloss in American Heritage Dictionary 4
Origin: + Greek glōssa, language, tongue.
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