Labials refer to consonant sounds that are produced by using the lips, such as "b," "p," "m," and "w." There are several synonyms for this term, including bilabials, which specifically refers to sounds that use both lips, such as "p" and "b." Labiodentals are another type of consonant sound that include the use of both the lips and teeth, such as "f" and "v." These sounds are produced by placing the lower lip against the upper teeth. Another synonym for labials is labiovelars, which are sounds produced by both the lips and the back of tongue, such as "kw" and "gw".