Cot-caught merger

The cot-caught merger is a sound change where the vowel in the word "cot" and the vowel in the word "caught" come to sound the same and make the words "cot" and "caught" sound alike. It is also called the lot-thought merger. This sound change occurs for many people in the United States, Canada, Scotland and Ireland.
For example, people who have the cot-caught merger say these pairs of words the same way, but people who don't have the cot-caught merger say these pairs of words differently.