[I saw this question somewhere else (where it wasn't answered at the time) but I don't remember where and I'm unable to find it.]

So there are a number of ancient and/or reconstructed languages that lack not only labiodental fricatives, but also other labial fricatives, for example:

None of the above languages have labiodental (or even other labial) fricatives. Is this a coincidence or is there any reason they lack labial fricatives?

  • Even Modern Japanese doesn’t have labial fricatives, except [ɸ] as an allophone of /h/ before /u/ (and occasionally in loan words, but I wouldn’t count those), so it’s not always just a matter of reconstruction or age. Classical and pre-Classical Greek also had no labial fricatives (the change /pʰ/ > /ɸ ~ f/ happened later on, in the Koine period). May 27, 2021 at 18:07
  • Probably it is just the instability of f-like sounds over time, they tend to disappear without a trace via an intermediate /h/-sound. Something that is completely gone without reflexes in the daughter languages cannot be reconstructed. May 27, 2021 at 23:02

1 Answer 1


In general, for any known language sound there is some probability that a given language will have that sound, so that the clicks are very rare sounds and [a] is a very common sound. Theoretically, you could say that the probability is N that a language would have any labial fricative, or M that it will have [ɸ], if only we had a uniform list of phonemes of human languages. However, we don't have such a database. It is a coincidence that that particular set of older languages do not have labial fricatives. Proto-Bantu, Proto-Salishan and proto-Semitic also do not have labial fricatives (caveat about Bantu below), also Menominee and Didinga do not have labial fricatives.

Fricatives are less frequent in human languages, compared to stops, because it is harder to identify them (their acoustic cues are not as robust). Labial fricatives are not the most difficult to identify ([θ] might have the honor there), but they are much more difficult to identify compared to sibilants (their characteristic spectrum is more diffuse and at a too-low frequency). What we don't know is whether [x] as a phoneme is statistically more-often attested compared to [f], or the opposite. It does seem that [f] is more frequent than [ɸ]. The evolutionary logic of this is that if there were [f] at some point, it could most easily change to something else like [h] or just get deleted, because it is hard to detect.

One should also exclude allophonic variants and only look at fricatives as phonemes. In many Bantu (and other) languages, there is a phonetic "fricative" [β] which may more properly be classified as an approximant, which is the result of weakening /b/ in some context. [f] developed allophonically in Hebrew and other Semitic languages, likewise.

  • While Proto-Semitic didn't have *f, I've seen it reconstructed for Proto-Afro-Asiatic, based mainly on evidence from Egyptian (and, admittedly, not much else).
    – Draconis
    May 28, 2021 at 1:35

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