I noticed that in Sanskrit (as well as in many Indo-Aryan languages), the vowel /a/ appears much more frequently than any other vowel. Many words have only have /a/ as a vowel.

Is there any reason behind this? Were the vowel distinctions in PIE (or for that matter, proto-Indo-Iranian) lost? If so, when?

  • 6
    PIE e, o, a all merged into Sanskrit a. You must know this, so I guess you're asking about a reason for these changes? I don't know the reason.
    – Greg Lee
    Feb 17, 2020 at 10:42
  • 2
    It seems to be so in Avestan too, so it's probably a proto-Indo-Iranian development.
    – Li Xinghe
    Feb 17, 2020 at 13:31
  • By "lost" do you mean they merged into a? or do you mean they were reduced to a? or did all other vowels besides a disappear leading to consonant clusters? Could you clarify what your suspicion is, so people can keep that in mind when answering? Feb 19, 2020 at 17:43
  • I mean the distinctions were lost.
    – Li Xinghe
    Feb 22, 2020 at 4:45

1 Answer 1


From Proto-Indo-European to Proto-Indo-Iranian it has been theorized that *e, *o, and the sometimes reconstructed *a all merged into *a (some exceptions such as Brugmann's law--*o > *ā in open syllables--apply). This probably happened sometime around the 3rd millennium BCE when the Indo-Europeans began to split up, with the Indo-Iranians moving towards the Eurasian steppe.

Why does this happen? It could be that the a in Sanskrit, which is [ə] or something thereabouts, is the "easiest" vowel sound to pronounce in that it requires minimal effort to shape the mouth. Because of that, vowels nearby may be inclined to evolve towards that sound. Of course, the same applies to Old Persian and Avestan.

This is not the most satisfactory explanation because it does not account for phenomena such as a turning into the harder-to-pronounce [ɔ] in Eastern Indo-Aryan, but it is generally difficult to account for phonological changes of this manner. This is likely the best we can do.

Interestingly, this is reflected in the Brahmic scripts used for Sanskrit and its descendant languages, which used a as the inherent vowel thereby avoiding writing it every time after a consonant.

  • 1. Perhaps it was the lack of vowels in the Brahmic script that caused errosion of vowels?! A lot speaks agaibst that, but it needs to be noted. 2. The reconstructions I am familiar with chiefly avoid vowels in roots and derive them rather from laryngeals that were largely lost themselves. Thesse did most often cause *e, *a, *o indeed. That warrants the question, phrased in the negative due to my ignorance about details, does the distribution of a not match those precisely, so that the laryngeals having merged is out of the question? Indeed I often saw a mere *H notated for PII.
    – vectory
    Feb 18, 2020 at 19:08
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    @vectory I honestly can't tell if you're trolling at this point. Proto-Indo-Iranian broke up millennia before the Brahmic scripts arose. The Brahmic scripts don't lack vowels, they just have a default a instead of a default ∅. If writing systems without vowels caused vowels to disappear from spoken language, the Semitic languages would have nothing but consonants by now. There's an enormous amount of evidence that Proto-Indo-European *o existed separate from *h₃ (the ablaut system most notably). The laryngeals did merge in Proto-Indo-Iranian, but the coloring effects happened…
    – Draconis
    Feb 20, 2020 at 3:19
  • …back in PIE or even "Proto-Indo-Anatolian" if you call that a separate stage. And as Aryaman said, the late-PIE short vowels *e *a *o (probably) all merged into *a in Proto-Indo-Iranian, so no, it doesn't match the distribution of the laryngeals.
    – Draconis
    Feb 20, 2020 at 3:22
  • Laryngeals indeed all merged in PII. @vectory no, the script idea doesn't work. Brahmi appeared around the 4th century BCE which was well past the posited dates for PII. Also, literacy was limited to a priestly class of society so I do not see it causing widespread linguistic change. Finally, Brahmi does mark every vowel except the a sound, which is inherent to a consonant unless explicitly removed. Brahmi is a very well-organized script that has no clear precursor (some speculate Amharic), so it is likely that is was created to fit the language rather than the other way around.
    – Aryaman
    Mar 7, 2020 at 0:51

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