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 IPA|ɔ̹ ɔ̜, 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. (See relative articulation.)

Types of rounding

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. 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 official 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. In standard Japanese, the back high vowel /u/ has no lip rounding at all (it is always [ɯ] ).

The northern Iroquoian languages have no labial consonants. They do have IPA|/w/, IPA|/ɡʷ/, and IPA|/kʷ/, but these do not involve noticeable rounding (protrusion) of the lips. It may be that they are purely velar IPA| [ɰ, ɡᶭ, kᶭ] , but it is also possible that they are compressed.

ee also

*List of phonetics topics
*Close front compressed vowel
*Close central compressed vowel
*Close back compressed vowel