Original sentence: The den-then merger is a phonemic merger of  as  that occurs in some varieties of nonstandard English.The merger occurs mainly in some varieties of Caribbean English, African American Vernacular English (AAVE), Scouse, Irish English and also occurs in Newfoundland
Edited sentence: The den-then merger is a mispronunciation of  as  that occurs in some varieties of nonstandard English.The merger is generally stigmatized and thought of as sounding lazy and uneducated.The merger is one of the well known characteristics of African American Vernacular English (AAVE).The merger occurs mainly in some varieties of Caribbean English, AAVE, Scouse, Irish English and also occurs in Newfoundland