Vowels can change from short vowels to long vowels in time

But from a diachronic perspective, what is happening?

Please fill in with some examples of vowels that have been prolonged and that have been used to reconstruct language families using the comparative method?

  • What I meant by "prolonged": From a short vowel to a long vowel. An example is from Norwegian. The word fɑstə is also (socio-linguistically) pronounced fɑ:stə. Can such changes be used to distinguish language-genealogy using the comparative method? – Flying Nov 21 '14 at 13:40
  • 2
    Compensatory lengthening is common; it can happen by removing consonants, as @YellowSky points out in Turkic, or simply by losing some consonantal feature that produced a lengthened vowel allophone while leaving the allophone, such as French bête, même from bestia, mesme. – jlawler Nov 21 '14 at 17:30
  • @jlawler This is not actually a very good example. The vowel in bête is not long. The circumflex is purely graphic. – fdb Feb 4 '15 at 19:47

It is not clear what you mean by "prolonged", but if you want to know how long vowels can appear in a language that earlier had none of them, one way of it is when a consonant between 2 vowels disappears and the vowels merge. The Turkic and Mongolian languages that have long vowels got them this way, the earliest Turkic and Mongolian languages had no short vs. long distinction. For example, the Old Turkic word oɣul (son) developed like this:

oɣul > oul > ool > oːl

And now in Altay, Tuvan, etc. it is oːl, with a long vowel, spelled оол.


The phrase "used to reconstruct language families using the comparative method" is not literally meaningful, since you can reconstruct linguistic forms or you can make hypotheses about the grouping of languages into families, but you can't reconstruct a family. I think you mean "used in the reconstruction of an earlier stage of a language". As example of that would be the derivation of long vowels in proto-Indo-European from the loss of earlier laryngeals. That would be a case of compensatory lengthening as Jlawler mentions. In addition to vocalic merger (with or without there having been an intervening consonant), there are various prosodic causes. The Norwegian case, which has a parallel in North Saami, involves a change in syllabification where VCCV could be parsed as V.CC or VC.CV, and the change is from non-branching onsets to branching onsets with no coda i.e. VC.CV -> V.CCV. A frequent instance of that is lengthening of vowels before NC clusters in Bantu. Another very common one is stress-related: stress may be assigned to some position, and that causes vowel lengthening (a number of Bantu languages, Mohawk, etc.). A third context for lengthening is "minimality" related, where monosyllables (typically) have to lengthen their vowel because every word has to have at least two moras (various Bantu, Arabic dialects).

Numerous historical questions are associated with lengthening, such as "does lengthening by such-and-such process require pre-existing phonemic vowel length", but you'd have to be more specific about what connection between lengthening and reconstruction you're asking about.

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