Labialisation

Labialisation (labialization) is a phonetic and phonological feature in which a sound is produced with simultaneous rounding of the lips. It is a secondary articulation that can accompany consonants or vowels, and it is commonly depicted in phonetic transcription with a superscript small w after the symbol, as in [tʷ] or [kʷ]. It also characterizes vowels that are produced with lip rounding.

In consonants, labialisation adds lip rounding to the primary articulation, creating labialized consonants. In some languages this is phonemic, meaning that a labialized versus a non-labialized variant distinguishes words; in others, it is allophonic or a coarticulatory effect that arises from surrounding vowels or context.

In vowels, labialisation refers to the rounding of the lips during vowel articulation. It can be an intrinsic property of the vowel (rounded vowels) or induced by neighboring segments. Some language systems contrast rounded and unrounded vowels, while others show lip rounding spreading from adjacent consonants or vowels.

Labialisation is often motivated by coarticulation and can arise historically when nearby vowels influence consonants, or vice versa. It is distinct from the place of articulation, as it concerns lip rounding as a secondary feature.