Rounding

From KneeQuickie

Rounding refers to the position of the lips during a vowel sound. Most languages only distinguish two lip positions: unrounded (pronounced with little lip movement) and rounded (pronounced with the lips squeezed together at the sides and opening wider in the centre, forming an "O" shape). Consonants can also be rounded, although this is more usually referred to as labialization.

The terms exolabial and endolabial are used to describe whether the inner or the outer surface of the lips are used for the rounding. Exolabial rounding uses the inner surface, making the lips pout; endolabial uses the outer surface. Back rounded vowels are normally exolabial, while front ones tend to be endolabial. Standard Swedish has both endolabial and exolabial [Y] phonemically, although the endolabial one (long u) is always long, while the exolabial one (short y) is always short. The endolabial vowel is traditionally written /}:/, because this is what it used to be, and still is in Norwegian and many dialects.

In the IPA, there are no diacritics to show rounding, since rounded and unrounded vowels have separate symbols. There are, however, diacritics to show lesser degrees of rounding: for instance, /ʊ̹/ would be a more rounded /ʊ/, and /ʊ̜/ would be less rounded. The X-Sampa equivalents are _O and _c respectively.

Z-Sampa has separate diacritics for exolabial (_W) and endolabial (_W\) rounding.