Labialization

Labialization is a secondary articulatory feature of sounds in some languages. Labialized sounds involve the lips while the remainder of the oral cavity produces another sound. The term is normally restricted to consonants. When vowels involve the lips, they are called rounded.

The most common labialized consonants are labialized velars. Most other labialized sounds also have simultaneous velarization, and the process may then be more precisely called labio-velarization. The "labialization" of bilabial consonants often refers to protrusion instead of a secondary articulatory feature velarization. [pʷ] doesn't mean [pˠ] although [w] refers to a labial–velar approximant.

In phonology, labialization may also refer to a type of assimilation process.