isogloss
/ˈaɪsəɡlɔs/
noun
- A line on a dialect map marking the boundary between areas that differ in a particular linguistic feature.
- The isogloss separates regions where people say 'soda' from those that say 'pop'.
- Multiple isoglosses can cluster together, forming a dialect boundary.
- Linguists drew an isogloss to show where the pronunciation of 'cot' and 'caught' merges.