Bilabial consonant in the context of "Assimilation (phonology)"

In phonetics, a homorganic consonant (from Latin homo- 'same' and organ '[speech] organ') is a consonant sound that is articulated in the same place of articulation as another. For example, [p], [b] and [m] are homorganic consonants of one another since they share the bilabial place of articulation. Consonants that are not articulated in the same place are called heterorganic.

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

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

Linguolabials or apicolabials are consonants articulated by placing the tongue tip or blade against the upper lip, which is drawn downward to meet the tongue. They represent one extreme of a coronal articulatory continuum which extends from linguolabial to subapical palatal places of articulation. Cross-linguistically, linguolabial consonants are very rare. They are found in a cluster of languages in Vanuatu, in the Kajoko dialect of Bijago in Guinea-Bissau, in Umotína (a recently extinct Bororoan language of Brazil), and as paralinguistic sounds elsewhere. They are also relatively common in disordered speech, and the diacritic is specifically provided for in the extensions to the IPA.

Linguolabial consonants are transcribed in the International Phonetic Alphabet by adding the "seagull" diacritic, U+033C ◌̼ COMBINING SEAGULL BELOW, to the corresponding alveolar or dental consonant. Pullum & Ladusaw (1996) additionally suggest these sound may be equivalently transcribed with the apical diacritic, U+033A ◌̺ COMBINING INVERTED BRIDGE BELOW, on the corresponding bilabial consonant. However, Olson et al. (2009:64) reject this transcription, as linguolabials may be articulated either apical or laminal. The labial consonants ⟨p᫥, m̼, v̼⟩ have also been used. The choice of the base consonant may depend on whether the author analyses the linguolabial as being phonologically labial or alveolar.