I am trying to understand the sound change that brought PIE *dent- to P.Gmc. *tanth-. Grimm's law seems to be the culprit for the consonant changes:

  1. Initial voiced stop /d/ devoiced to /t/
  2. Terminal voiceless stop /t/ brought to voiceless fricative /θ/

I can understand the change in #1 (this is assimilation, correct?), but what's the reason for the stop -> fricative change in #2?

  • 2
    I'd be surprised if someone could give you an easy answer.
    – Alex B.
    Commented Nov 11, 2012 at 19:09
  • 3
    Just plain laziness.
    – Mitch
    Commented Nov 17, 2012 at 0:56

4 Answers 4


Wikipedia's page on lenition seems to suggest that a /t/ -> /θ/ change can actually come from a /t/ -> /tθ/ (affrication) -> /θ/ (spiratization) change.

I don't know enough to confirm or deny that this is what Grimm's law describes. I assume if this were true the /tθ/ step would be part of the law.

  • 4
    The reference to lenition is appropriate. Note that this kind of change is widespread in languages (offhand I can think of it in Hebrew and all the modern Celtic languages). It is also in progress in some English dialects: in Scouse unvoiced stops (at least, /k/ and /t/) are heavily aspirated, often going as far as the affricates to /kx/ and /ts/, and sometimes losing the plosive part completely (/x/ and /s/).
    – Colin Fine
    Commented Nov 12, 2012 at 1:04

Well, assuming that it went through the way the Grimms and their successors put it -- and not, for instance, the way the Glottalic Theory puts it -- Grimm's Law is a chain shift of three different consonant classes:

  1. PIE voiced aspirated stops changed to Germanic plain voiced stops
    • PIE *bher- --> Eng bear
  2. PIE voiced stops changed to Germanic voiceless stops
    • PIE *dent- --> Eng tooth
  3. PIE voiceless stops changed to Germanic fricatives
    • PIE *ten- --> Eng thin

Nobody knows which happened first, or when, or by which group. But the changes appear in all Germanic languages, so they must have been complete after Proto-Germanic separated from I-E, but before it split up. These changes happened only in mode, never in position -- i.e, dentals changed to dentals, labials changed to labials, etc.

The one exception is the PIE labiovelar phonemes -- *ghʷ, *gʷ, *kʷ. Labiovelars were lost in Greek, and smeared all over the spectrum, from labial to velar. Germanic and Latin, however, kept some but not all labiovelars (that's what the Romans used QU for -- /kʷ/ was a separate phoneme from /k/ in classical Latin; and that's also where all the English wh-words came from).

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    "/kʷ/ was a separate phoneme from /k/ in classical Latin;" - what is the proof that it was separate from /kw/?
    – Anixx
    Commented Nov 16, 2012 at 8:19
  • 1
    @Anixx: It isn't separate from /kw/ but is often thought to be a single phoneme because it doesn't trigger a heavy syllable for accent or poetry purposes, and it doesn't evolve to /ku/ (which /w/ after a consonant usually does). Same arguments are made for treating /gw/ as a single phoneme. Commented Oct 15, 2013 at 5:38
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    "Nobody knows which happened first" - however, they couldn't have happened in the order listed, or all the stops would have ended up as fricatives. (That is, it's possible that 2 began later than 1 but before 1 was complete, and so on, but it's impossible that 1 first ran its course, then 2, then 3.)
    – TKR
    Commented Nov 6, 2013 at 3:56
  • That's one way of looking at it. But it might well have been two dialectal versions that collided and merged. Or it might have been, as the Glottalic theory has it, that the change happened everywhere except Germanic (and Armenian, I think), so all the other languages are the innovators and Germanic is the conservative one. Duelling theories at this point, though. Maybe they'll find a transcription that'll settle the problem; but probly not.
    – jlawler
    Commented Nov 6, 2013 at 18:23

I would really give not an answer but somewhat refusal for the question (despite the question is really good). Currently, the common position is to expand so-called "principle of the arbitrariness of the sign" also to language changes, i.e. you could guess which changes are impossible (for rude example, it's unlikely for any IE language to unify all vowels to a single one), but when you have multiple possible choices which doesn't break language structure at any level, you can't predict which one will happen. For the change you mean, if it had took place at all, it 1) moved sounds to neighbour ones, 2) didn't break phonologic relations between related sounds (d[h] - t[h] - t), and this is enough to allow it in theory.

If you become able to explain in most cases why an allowed change happens, this would be the second main discovery through the diachronic linguistic history. (The first one was simply the fact that languages can originate from a common source.) Currently, linguistics has found multiple examples for special cases, as substrate/superstrate/neighbour language affecting, but not a common rule. You can compare this with evolution theory: there are prohibited mutations which give an unviable being, so they can't happen, and are allowed mutations, which can't be predict due to really stochastic source.

The best rule for this I've seen currently is from the typology which counts probability of some change. For example, change /t/ -> /θ/ is known from numerous languages (the closest examples are modern Greek and Castilian, but for /d/ -> /ð/), so it's very likely. Also, pressure of need to distinguish /t/ and /tʰ/ could move any of them to another sound, to make the distinction more expressed (and hence easier to detect). This could be the "narrow" answer to your question: the move was done to keep useful difference between phonemes. But it doesn't give a reason for the whole move, described by Grimm's law.

(Please also note that Glottalic theory says that the Germanic languages really keep the initial PIE series distribution, with minor changes.)

  • The Glottalic theory is more or less discredited by now. Commented Oct 15, 2013 at 5:38
  • @UrbanVagabond: it's "discredited" no more on less than traditional "theory" which wasn't initially grounded at all. The most neutral POV is too consider them in parallel without any strict preference to either.
    – Netch
    Commented Oct 16, 2013 at 6:43
  • That isn't true. The traditional t - d - dh theory is well-grounded using the comparative method. The glottalic theory isn't. And it is discredited in that the large majority of Indo-Europeanists have rejected it. I think the only ones who don't are at Leiden, e.g. Frederik Kortlandt, who has quite idiosyncratic views that are not generally accepted. Commented Nov 6, 2013 at 3:21
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    BTW the fact that all daughter languages eliminated the typologically uncharacteristic t - d - dh system, but in 4 or 5 different ways, is actually an argument in favor of this reconstruction. The glottalic theory is claimed to be more typologically natural but for precisely this reason it would be unlikely to have shifted independently in all daughters. Commented Nov 6, 2013 at 3:32
  • @UrbanVagabond: all Slavic languages eliminated reduced vowels (ъ, ь) in different ways. And Slavic vowel system definitely was typologically rare. Is that an argument against their existence in common Slavic, despite written evidences?;) I scare to imagine what reconstruction would be provided if we hand't OCS books seen...
    – Netch
    Commented Nov 7, 2013 at 6:20

Jon -- you're a bit confused when you say "initial" vs. "terminal". All the Grimm's Law changes happened in all positions (except directly after an obstruent).

As others have mentioned, it's impossible to say for sure why a particular change happens, but there are various plausible theories, e.g.:

  1. An initial chain shift d -> t, t -> th (aspirated stop) is extremely common. Aspiration of initial voiceless stops is common, and if that happened then d would naturally shift to t through economy of effort, and in turn dh would shift to d. Aspirated stops changing to fricatives are also common (e.g. happened in Greek).
  2. It's also possible that t shifted directly to a fricative; this is more likely to have begun intervocalically and expanded to other positions. If this happened, then d -> t followed by dh -> d would also be natural changes.
  3. It could have also been a push chain. The t - d - dh system is typologically very rare and obviously dispreferred, and so there would be pressure to eliminate the dh. If dh started to shift to d, then either it would merge with d or force a chain shift. Both solutions are seen (dh -> d in Balto-Slavic, Celtic, Iranian, etc.; chain shift in Germanic and Armenian).

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