There are many examples that show that two phones [v] and [b] are related:

b v Meaning
Old English to New English * habban have have
Middle Persian to New Persian varan baran rain
Middle Persian to New Persian vehtar behtar better

*Related to German haben

Besides, there is another relation between these phones.In the Cyrillic alphabet, the sign B is pronounced [V].

The phonetic characteristics of these two phones is as follows:

Place of articulation Manner of articulation
v Labiodental Fricative, Voiced
b Bilabial Stop, Voiced

Given that they don't have much in common, I'd like to know:

  • How is the connection between these phones justified?
  • 10
    The reason Cyrillic B represents /v/ is that the Cyrillic alphabet is based on Greek pronunciation from a time when /b/ had already shifted to /v/ (or at least /β/). Note that B (beta) is also pronounced /v/ in Modern Greek (where its name is vita). It’s likely that most cases of b>v or v>b go through /β/ as an intermediate stage (cf. Spanish where this is the synchronic stage currently). Commented Feb 26, 2021 at 11:53
  • 2
    English did not develop out of German; rather, both share a common ancestor.
    – Miztli
    Commented Feb 26, 2021 at 12:14
  • 4
    If you don’t bother closing the lips when making a /b/, you make a /β/. If you then don’t bother using the top lip, only the bottom one, you make a /v/, which is acoustically similar to /β/ anyway. These are very frequent developments worldwide (along with the unvoiced counterpart, /p/>/ɸ/>/f/). You can keep leniting it further to /h/, then nothing. Commented Feb 26, 2021 at 12:36
  • 1
    Does this answer your question? Change of B > W in casual speech Commented Feb 26, 2021 at 13:27
  • 1
    Middle Persiam wārān and wehtar had /w/ not /v/.
    – fdb
    Commented Feb 26, 2021 at 21:55

1 Answer 1


The differences between [b] and [v] are fairly trivial between from a historical and phonetic perspective. The count of shared categories in the IPA chart isn't a good way of judging similarity (and the IPA doesn't claim to embody all relevant concepts of "category"). They are voiced oral labials: you can add "-dental" or "bi-" to be more precise. They are so similar that it is often hard to distinguish them.

Historical change operates by a series of changes, not leaps from Proto-X to Modern Y, and generally the progression is from [b] to something like [β] and [ʋ]. In some dialects of Tigrinya, /b/ becomes "[β]" in post-vocalic position, and this is optional but usually happens, but where it is extremely difficult to sharply categorize tokens as having [b] versus [β] (there is no contrast, you just have to look closely at the waveform). The difference has to do with the timing of the closure going into the consonant plus the total duration of the consonant, and very often it's a coin toss whether [b] or [β] is a better transcription.

  • de babeporms, we habe to look closer. (I got sinusitis)
    – vectory
    Commented Mar 1, 2021 at 10:59
  • What about the notion that aggriculture and soft food caused underbite which biased /p/ to /f/. Same for /b v/?
    – vectory
    Commented Mar 1, 2021 at 11:06

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