Answer:
An isogloss is a geographical area that uses a particular feature when they speak and that other surrounding places do not use.
Chicago is an example of an isogloss because people in Chicago tend to pronounce the /r/ after a vowel while the neighboring areas do not.
Step-by-step explanation:
Isoglosses are areas where a word, sound, or phrase is pronounced differently or has a different meaning in comparison with other cities or places that are close to this one. It is part of the accent and the culture of that region.
If we think of Chicago, we can see that people there pronounce the /r/ after a vowel while the surrounding areas do not pronounce it. Some examples are words such s torn or harm.