Vowel shifts are systematic changes in the pronunciation of vowel sounds within a language over time. These shifts can affect how words are spoken and can lead to significant differences in dialects. A well-known example is the Great Vowel Shift that occurred in English during the late Middle Ages, which altered the pronunciation of many long vowels. Such changes can result from various factors, including social influences, geographical separation, and language contact. Vowel shifts can create distinctions between regional accents and contribute to the evolution of languages, making them dynamic and ever-changing over time.