A vowel shift refers to a systematic change in the pronunciation of vowel sounds within a language over time. This phenomenon can affect how words are spoken and can lead to significant differences in accents and dialects. One well-known example is the Great Vowel Shift, which occurred in English during the late Middle Ages, dramatically altering the pronunciation of long vowels. Vowel shifts can occur for various reasons, including social, geographical, and linguistic influences. They often reflect changes in a community's speech patterns and can contribute to the development of new dialects. Understanding vowel shifts helps linguists study language evolution and the relationships between different languages.