Labialization


 * "Lip rounding" redirects here. See Roundedness'' for the lip rounding of vowels.

Labialization is a secondary articulatory feature of sounds in some languages. Labialized sounds involve the lips while the remainder of the oral cavity produces another sound. The term is normally restricted to consonants. When vowels involve the lips, they are called rounded.

The most common labialized consonants are labialized velars. Most other labialized sounds also have simultaneous velarization, and the process may then be more precisely called labio-velarization.

Labialization may also refer to a type of assimilation process.

Where found
Labialization is the most widespread secondary articulation in the world's languages. It is phonemically contrastive in the Northwest Caucasian, Athabaskan, and Salishan language families, among others. This contrast is reconstructed also for Proto-Indo-European, the common ancestor of the Indo-European languages.

American English has three degrees of labialization: tight rounded, slight rounded , and unrounded, which in vowels is sometimes called 'spread'. These secondary articulations are not universal. For example, French shares the English slight rounding of while Russian does not have slight rounding in its postalveolar fricatives.

Types of labialization
Out of 706 language inventories surveyed by, labialization occurred most often with velar (42%) and uvular (15%) segments and least often with dental and alveolar segments. With non-dorsal consonants, labialization may include velarization as well. Labialization is not restricted to lip-rounding. The following articulations have either been described as labialization, or been found as allophonic realizations of prototypical labialization:


 * Labial rounding, with or without protrusion of the lips (found in Navajo)
 * Labiodental frication, found in Abkhaz
 * Bilabial frication, found in Ubykh
 * Bilabial trill, found in Ubykh
 * Bilabial plosion, found in Ubykh
 * "Labialization" (,, and ) without noticeable rounding (protrusion) of the lips, found in the Iroquoian languages. It may be that they are compressed.
 * Rounding without velarization, found in Shona and in the Bzyb dialect of Abkhaz.

Eastern Arrernte has labialization at all places and manners of articulation; this derives historically from adjacent rounded vowels, as is also the case of the Northwest Caucasian languages. Marshallese also has labialization at all places of articulation except for coronal obstruents.

Transcription
In the International Phonetic Alphabet, labialization of velar consonants is indicated with a raised w modifier (Unicode U+02B7), as in. (Elsewhere this diacritic generally indicates simultaneous labialization and velarization.) There are also diacritics, respectively, to indicate greater or lesser degrees of rounding. These are normally used with vowels, but may occur with consonants. For example, in the Athabaskan language Hupa, voiceless velar fricatives distinguish three degrees of labialization, transcribed either or.

The Extensions to the IPA has two additional symbols for degrees of rounding: Spread and open-rounded. It also has a symbol for labialdentalized sounds,.

If precision is desired, the Abkhaz and Ubykh articulations may be transcribed with the appropriate fricative or trill raised as a diacritic:, , ,.

For simple labialization, resurrected an old IPA symbol,. However, their chief example is Shona sv and zv, which they transcribe and  but which actually seem to be whistled sibilants, without necessarily being labialized. The open rounding of English is also unvelarized.

Labial assimilation
Labialization also refers to a specific type of assimilatory process where a given sound become labialized due to the influence of neighboring labial sounds. For example, may become  in the environment of, or  may become  in the environment of  or.

In the Northwest Caucasian languages as well as some Australian languages rounding has shifted from the vowels to the consonants, producing a wide range of labialized consonants and leaving in some cases only two phonemic vowels. This appears to have been the case in Ubykh and Eastern Arrernte, for example. The labial vowel sounds usually still remain, but only as allophones next to the now-labial consonant sounds.