Why does PIE *weydtos give PGmc wīsaz not wīssaz?

compare Pgmc *stassiz, *gawissiz, *kwissiz

  • my guess would be that the preceding long vowel had something to do with it (the other examples all have a short vowel before the ss), but I don't have any particular source or other supporting evidence
    – Tristan
    May 4, 2022 at 17:25
  • 1
    @Tristan You’re absolutely right – it’s a well-established development in Germanic (I added an answer which has more details). May 4, 2022 at 20:02

1 Answer 1


It probably did, but one of the last phonological changes that happened to create what we call ‘Proto-Germanic’ was that long *ss was reduced to short *s after long vowels or diphthongs. More controversially (but no less correctly if you ask me), this didn’t apply to just *s(s), but to any geminate, resulting in the loss of overlong syllables in Proto-Germanic. This latter, less canonical, viewpoint is part of Kluge’s Law.

Examples with *ss include, giving a (Post-)PIE form a pre-PG form, and the ‘classical’ PG form:

  • *h₁ēd-tos > *ēssaz > *ēsaz ‘food, carrion’
  • *koi̯d-tis > *haissiz > *haisiz ‘command’ (same root as *haitaną ‘call’)
  • *u̯ei̯d-tos > *wīssaz > *wīsaz ‘wise’

Examples with other consonants include:

  • *dʰeu̯bʰ-no- > *deupna- > *deuppa- > *deupa-
  • *dʰei̯gʰ-[n?]o- > *dīkka- > *dīka-

There aren’t many exactly parallel cases, but there are some. As you can read about briefly in the Wikipedia article linked to above - and in more detail in Guus Kroonen’s PhD dissertation – the issue has been mired in controversy for over a century.

Not, however, when it comes to *ss becoming *s after long vowels and diphthongs – that bit is pretty universally accepted.

  • how does this shortening of overlong syllables relate to the overlong vowels? Would it have to have occurred before the formation of such vowels?
    – Tristan
    May 5, 2022 at 8:43
  • 1
    @Tristan That’s a good question. Given how little we know about the actual practicalities of overlong vowels in PG, I don’t think we can say for sure. Personally, I suspect that the single overlong vowels did indeed come about later and weren’t necessarily a thing for very long before they were then shortened and merged with the regular long vowels (except word-finally). At the stage just prior to ‘classical’ PG when overlong syllables were lost, I think the ‘overlong’ vowels were likely still disyllabic sequences of long + short identical vowel. May 5, 2022 at 9:07

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