That sound may also be transcribed as an advanced labiodental approximant ⟨ʋ̟⟩, in which case the diacritic is again frequently omitted, since no contrast is likely.

[1][2] It has been proposed that either a turned ⟨β⟩, reversed ⟨β⟩ or affricate ⟨βθ⟩ can be used as a dedicated symbol for the bilabial approximant, but despite occasional usage none of them have gained general acceptance.

[4] Proto-Germanic[5] and Proto-Italic[6] are also reconstructed as having had this contrast, albeit with [β] being an allophone for another consonant in both cases.

In Bashkir language, it is an intervocal allophone of /b/, and it is contrastive with /w/: балабыҙ [bɑɫɑˈβɯð] 'our child', балауыҙ [bɑɫɑˈwɯð] 'wax'.

The bilabial fricative is diachronically unstable (likely to be considerably varied between dialects of a language that makes use of it) and is likely to shift to [v].