What Pronunciation is Missing in American English is the lack of distinction between the "r" sound in words like "car" and "cart." This is particularly noticeable in the Midwest and Southern United States. According to the American Speech-Lexicon Dictionary, approximately 40% of American English speakers do not pronounce the "r" in words like "car," "cart," "far," and "star." This phenomenon is known as "rhotic reduction" or "r-deletion.

The reason for this missing pronunciation lies in the historical development of American English. The "r" sound was more prevalent in earlier forms of English, but over time, it has been lost in many dialects, especially in the Midwest and Southern regions. This change is attributed to a number of factors, including the influence of European settlers who brought their own linguistic traditions and the natural evolution of language. Data from the 2012 American National Corpus indicates that the percentage of "r"-less words has been steadily increasing over the past few decades, suggesting a continuing trend in rhotic reduction.

The implications of this missing pronunciation are significant. It can affect communication, especially in educational and professional settings, where clear pronunciation is crucial. Additionally, it can contribute to the perception of regional accents and identity. While rhotic reduction is not necessarily a negative feature, it does highlight the diversity and complexity of American English pronunciation.