Bilabialis

Bilabialis is a Latin-derived term meaning “of two lips.” In scholarly usage it appears primarily in two domains: phonetics and anatomy. In modern terminology the more common form is bilabial, used to describe structures or sounds involving both lips; bilabialis is encountered mainly in older texts or Latinized descriptions.

In linguistics, bilabial refers to sounds produced with the contact or close approximation of the upper and lower lips. Common bilabial consonants in many languages include the voiceless and voiced stops p and b, and the nasal m. Some languages also feature bilabial fricatives or approximants; the latter may be described as labial or bilabial in certain analyses. The bilabial place of articulation is typically contrasted with other places of articulation such as labiodental or dental.

In anatomy, there is no widely recognized separate muscle named bilabialis. Movements of the lips are produced by coordinated action of several muscles, primarily the orbicularis oris, which encircles the mouth to close or protrude the lips, along with surrounding muscles such as the zygomaticus, levator labii superioris, and depressor labii inferioris. Some historical or Latinized descriptions may refer to groups of lip muscles as “musculi bilabiales,” but this is not a standard modern term; contemporary anatomy usually names the individual muscles rather than a unified bilabial muscle.

Etymology: bilabialis derives from bi- “two” + labialis from labium, meaning lip. See also bilabial, lips, and phonetics.