unrounded

When a (back) rounded vowel is pronounced, the lips form a circular opening that is typically wider or smaller according to how open or close the vowel is, while unrounded vowels are pronounced with the lips either spread or relaxed (neutral between spread and rounded). The degree of lip-spreading also correlates with the height of the vowel. In most languages, front vowels are spread and back vowels rounded; acoustically, this helps distinguish back vowels from front. However, some languages, such as French and German, contrast rounded and unrounded front vowels, and others, like Vietnamese, contrast rounded and unrounded back vowels. Turkish contrasts rounded and unrounded among both front and back vowels. The kind of rounding typically found with front and back vowels differs, though this detail is not commonly specified in descriptions of languages unless it's atypical.