The voiced bilabial fricative is a type of consonantal sound, used in some spokenlanguages. The symbol in the International Phonetic Alphabet that represents this sound is ⟨β⟩ (or more properly ⟨ꞵ⟩), and the equivalent X-SAMPA symbol is ⟨B⟩. The symbol ⟨β⟩ is the Greek letterbeta. This symbol is also sometimes used to represent the bilabial approximant, though that is more clearly written with the lowering diacritic, that is ⟨β̞⟩. Theoretically, it could also be transcribed as an advanced labiodental approximant⟨ʋ̟⟩, but this symbol is hardly (if ever) used in this manner. The bilabial fricative is diachronically unstable and is likely to shift to [v]. In the English language, this sound is not used, but can be made by approximating the normal "v" sound between the two lips.
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