bilabialen

Bilabialen are a class of consonants articulated with both lips. The term bilabial derives from Latin bi- meaning two and labial meaning lip. In phonetics, bilabials typically include the stops p and b, the nasal m, and the approximant w, though some analyses treat w as labio-velar rather than strictly bilabial.

Articulation: The defining feature is that both lips participate in the constriction of the vocal tract. The most common bilabial stops are p (voiceless) and b (voiced), followed by the bilabial nasal m. The bilabial approximant w is produced with rounding of the lips and some retraction of the tongue toward the velum; in some languages it is analyzed as labio-velar rather than strictly bilabial.

Distribution: Bilabials are among the most widespread consonants across languages. They often appear at syllable onsets and can contrast in voicing, nasalization, and rounding. Many languages also have bilabial fricatives or approximants in their inventories, such as a voiced bilabial fricative β or a voiceless ɸ, though these are less common.

Phonological behavior: Bilabials exhibit typical allophony, such as aspiration for the voiceless p in stressed syllables, and may undergo assimilation, for example lip rounding spreading to neighboring vowels. Their relative articulatory simplicity contributes to their ubiquity in world languages.