Roundedness
In
phonetics,
vowel roundedness refers to the amount of rounding in the
lips during the articulation of a
vowel. That is, it is vocalic
labialization. When pronouncing a
rounded vowel, the lips form a circular opening, while
unrounded vowels (also called
spread vowels) are pronounced with the lips relaxed. In most languages,
front vowels tend to be unrounded, while
back vowels tend to be rounded. But some languages, such as
French and
German, distinguish rounded and unrounded front vowels of the same
height, while
Vietnamese distinguishes rounded and unrounded back vowels of the same height.
When consonants are rounded, they are called
labialized.
In the
International Phonetic Alphabet vowel chart, rounded vowels are the ones that occur on the right in each pair of vowels. There are also diacritics, respectively , to indicate greater or lesser degrees of rounding. The 'more' and 'less rounded' diacritics are sometimes also used with consonants to indicate degrees of labialization. For example, in the
Athabaskan language Hupa,
voiceless velar fricatives distinguish three degrees of labialization, transcribed either or . The
Extended IPA has two additional symbols for degrees of rouding: Spread and open-rounded .
 |
Lack of rounding, endolabial rounding and exolabial rounding, as portrayed by a speaker of Swedish. |
There are two types of vowel rounding: endolabial, or
compressed, and exolabial, or
protruded.
In endolabial rounding, the corners of the mouth are drawn slightly together and the lips may be compressed horizontally, but the lips do not protrude and only their outer surface is exposed. In exolabial rounding, the lips protrude like a tube, as when
kissing; the inner surface of the lips is exposed. Usually, back rounded vowels are exolabial, while front rounded vowels are endolabial. However, in
Japanese, the back high vowel is endolabial.
Swedish is unusual in that dialects of it make a
phonemic distinction between the two types, having unrounded, endolabial, and exolabial front
close-mid vowels. Some varieties of
Dutch make the same distinction. There is no dedicated IPA diacritic to represent this contrast, and without disambiguation both the word "rounded" and the symbols for the rounded vowels are understood to refer to exolabial rounding.
The northern
Iroquoian languages have no
labial consonants. They do have , , and , but these do not involve noticeable rounding (protrusion) of the lips. It may be that they are purely
velar , but it is also possible that they are compressed. It is not known how this might relate to the labialization distinction in
Hupa.
*
List of phonetics topics*
Close front compressed vowel*
Close central compressed vowel*
Close back compressed vowel
