Labial consonants are those consonants articulated with the lips. This place of articulation is further divided to a number of subtypes:
- bilabial: consonants articulated with both lips
- labiodental: articulated with the lower lip against the upper teeth
- linguolabial: articulated with the tongue against the upper lip (may also count as coronal consonants)
- dentilabial: articulated with the lower teeth against the upper teeth
- labioalveolar: articulated with the lower lip against the alveolar ridge
Any contrasts between these types are highly rare though, and most languages (natural or constructed) can be analyzed as only having a single labial place of articulation. The labial stops, nasal and trill normally default to bilabial [p, b, m, ʙ], while the fricatives and flap have a tendency to be realized as labiodental [f, v, ѵ] (though the bilabial counterparts are not very rare either). A contrast between bilabial and labiodental fricatives is known to appear in some Bantu languages.
Labioalveolar and dentilabial consonants are typically only found in disordered speech.
The IPA provides a single basic series of labial consonant symbols, assumed to be bilabial by default, as well as additional labiodental basic symbols for the fricatives and flap (see above), plus the nasal /ɱ/. Other labial consonants can be transcribed by diacritics, e.g:
- [p̪]: labiodental voiceless stop
- [p̼] or [t̼]: linguolabial voiceless stop
- [p͆]: dentolabial voiceless stop
- [p͇]: labioalveolar voiceless stop