Labial consonants are consonants in which one or both lips^[1] are the active articulator^[2]. The two common labial articulations are bilabials^[3], articulated using both lips, and labiodentals^[4], articulated with the lower lip against the upper teeth, both of which are present in English^[5]. A third labial articulation is dentolabials^[6], articulated with the upper lip against the lower teeth (the reverse of labiodental), normally only found in pathological speech. Generally precluded are linguolabials^[7], in which the tip of the tongue^[8] contacts the posterior side of the upper lip, making them coronals^[9], though sometimes, they behave as labial consonants.

The most common distribution between bilabials and labiodentals is the English^[5] one, in which the nasal^[10] and the stops^[11], [m], [p], and [b], are bilabial and the fricatives^[12], [f], and [v], are labiodental. The voiceless bilabial fricative^[13], voiced bilabial fricative^[14], and the bilabial approximant^[15] do not exist as the primary realizations of any sounds in English^[5], but they occur in many languages. For example, the Spanish^[16] consonant written b or v is pronounced, between vowels, as a voiced bilabial approximant^[17].

Lip rounding, or labialization^[18], is a common approximant^[19]-like co-articulatory^[20] feature. English /w/ is a voiced labialized velar approximant^[21], which is far more common than the purely labial approximant^[15] [β̞]. In the languages of the Caucasus^[22], labialized dorsals^[23] like /kʷ/ and /qʷ/ are very common.

Very few languages, however, make a distinction purely between bilabials^[3] and labiodentals^[4], making "labial" usually a sufficient specification of a language's phonemes^[24]. One exception is Ewe^[25], which has both kinds of fricatives, but the labiodentals are produced with greater articulatory force.

Lack of labials

While most languages make use of purely labial phonemes, a few generally lack them. Examples are Tlingit^[26], Eyak (both Na-Dené^[27]), Wichita (Caddoan^[28]), and the Iroquoian languages^[29] except Cherokee^[30].

Many of these languages are transcribed with /w/ and with labialized consonants^[18]. However, it is not always clear to what extent the lips are involved in such sounds. In the Iroquoian languages, for example, /w/ involved little apparent rounding of the lips. See the Tillamook language^[31] for an example of a language with "rounded" consonants and vowels that do not have any actual labialization. All of these languages have seen labials introduced under the influence of English.

See also

• Labialization^[18]
• Index of phonetics articles^[32]

References

• Ladefoged, Peter; Maddieson, Ian (1996). The Sounds of the World's Languages. Oxford: Blackwell. ISBN 978-0-631-19815-4.
• McDorman, Richard E. (1999). Labial Instability in Sound Change: Explanations for the Loss of /p/. Chicago: Organizational Knowledge Press. ISBN 0-9672537-0-5.