Phonological change refers to the evolution of sounds in a language over time. This can involve shifts in pronunciation, the addition or loss of sounds, or changes in how sounds interact with each other. Such changes can occur due to various factors, including social influences, language contact, and the natural progression of speech. An example of phonological change is the Great Vowel Shift, which affected the pronunciation of long vowels in Middle English during the late 15th century. This shift significantly altered the way words were pronounced, leading to the modern English vowel system we recognize today.