The Great Vowel Shift mainly altered which Middle English sounds?

The Great Vowel Shift mainly altered long vowels in Middle English. Between roughly the 15th and 17th centuries, the pronunciation of the long-vowel system changed dramatically as English moved toward its Early Modern form.

Many close long vowels were raised, while the highest vowels developed into diphthongs. Thus Middle English vowel qualities in words such as bite, house, and meet came to differ substantially from their modern pronunciations. The changes were not one single event but a chain of related shifts, especially prominent in southern England.

The shift helps explain why English spelling often preserves pronunciations that no longer match the spoken language. Spelling had become relatively standardized before the sound changes were complete, so forms such as “name,” “meet,” and “bite” retain historical clues.

A common mix-up is to treat the Great Vowel Shift as primarily a change in consonants or short vowels. Some consonants became silent during related periods, but the defining development was the restructuring of the long-vowel system; regional varieties also followed the process differently.