Is there a specific reason for which diphthongs in German and English words like "mein" and "like" arose? It seems to be a pretty common phenomenon, but somehow it seems to be limited to Germanic languages. The same question could apply to "Haus" and "House" etc.

3 Answers 3


The kind of diphthongization found in Germanic as exemplified by "like" and "mein" (or the reverse order of elements, as in a rising diphthong) is extremely common in Germanic, but not limited to Germanic. It also arises in the history of Spanish and Italian (dialects), Old French and Quebec French; Finnish (dialectally) and the Saami languages; Sakha (Turkic); Slovak; Guerze; Kɔnni; Yokuts, and Lama. Except in the puzzling case of Lama and possible some other Gur languages where only short vowels diphthongize, it happens to long vowels.

We typically notice these processes when they are firmly established some hundreds of years after the diachronic tendencies have started, but I think it is possible for linguists to document these tendencies now and see how they work out in a few centuries. For example, from the nature of the North Saami diphthongizations, comparison with corresponding processes in other Saami languages, and an investigation of the realization of the excrescent vowel attested in "extra-long" consonant clusters (bár(ə)tni), a good case can be made that [uo, ie, ea, oa] are a development from [uə iə eə oə], earlier [u: i: e: o:]. There is is a similar process ongoing in Norwegian where [e] is not pronounced as a monophthong, it is a phonetic diphthong somewhere in the range of [ɛa] or [ɛə]. Although it is known that American English [ɪ,ʊ,ɛ,ɔ] are usually realized as phonetic diphthongs, this is a low-level detail of pronunciation that doesn't yet enter into the phonology, so it is often ignored.

It is likely that this is a recurring instance of "gesture alignment", where the articulatory gesture characterizing a kind of sound is aligned more to the left, or to the right, within its domain. This is quite well known in the case of pitch, where the most common trend is displacement to the right. Applied to a vowel, if the articulatory gestures characterizing [i] are more timed towards the beginning of the syllable, you will tend to get an [iə]-like output and if they are more timed towards the end, you will get an [əi]-like output. The correlation with long vowels is explained by the fact that they have longer duration and therefore more time within which a perceptible distinct vocalic articulation can be realized. I do not know why Bantu languages so resolutely avoid long-vowel diphthongization.

  • I think you meant [i] near the end rather than [u]?
    – TKR
    Dec 29, 2018 at 20:19

True. The other long vowels were raised but /iː/ and /uː/ can't be raised further. The diphthongization was surely partly a strategy to differentiate the raised /eː : oː/ from /iː : uː/ (chain shifts/ push/pull chain).

Why these whole significant vowel shifts happened though is a good question. It seems that vowels in Germanic languages are very unstable, which leads to the Germanic languages having very many vowel qualities. This may be related to the Germanic word stress.

  • But why is there a need to differentiate in the first place?And could you please elaborate the part about the stress?
    – X30Marco
    Dec 29, 2018 at 13:28
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    If you don't differentiate sounds you can't transmit information. Speaking is similar to transmitting information digitally only base-40-ish instead of base-2. A computer distinguishes a one and a zero by different voltages, speech sounds are distinguished by sound frequencies. If 1 and 0 are the same, you can't transmit information anymore. Dec 29, 2018 at 14:07
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    Proto-Germanic switched from a Proto-Indo-European accent pattern to a very predictable strong stress accent on the first syllable of a word (stem). In all living Germanic languages the unstressed syllables have then become simplified in some way. In most very drastically and often up to an apocope of the final syllable. Before being simplified the final syllables could have an influence on the stressed syllables (Umlauts as foot – feet, de. Fuß – Füße, nl. vallen – vellen). Those were early changes clearly influenced by the stress accent. Dec 29, 2018 at 14:16
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    Without the stress difference between syllables, the weakly stressed syllables wouldn't have been simplified and we wouldn't have ended up with Umlauts and other additions to the vowel inventory. The raising and diphthongization of vowels is not as easily explained by the stress but it is a common denominator in the Germanic languages that has had its influence on the vowels. Dec 29, 2018 at 14:19

Diphthongs are not limited to Germanic languages. It is pretty common in the languages of the world.

I can cite four phonetic aspects that lead to the outbreak of diphthongs. First of all, there are the diphthongs stemming from long vowels. This diphthongization is found in English (see: https://www.ling.upenn.edu/~kroch/courses/lx310/handouts/handouts-09/ringe/gvs-revised.pdf)

The other origin comes from the fall of a consonant. This lost consonant has allowed two vowels to merge together and if they have different qualities, they became diphthongs. This consonant can also be vocalized bringing about the same thing. Such a evolution can be found in Riffian (see: http://www.academia.edu/29199244/Tarifiyt_Long_Vowels_and_Diphthongs_Independent_Phonemes_or_Simple_Phonetic_Variants_of_the_Basic_Amazighe_Vowels_2004_)

The third case is when a vowel is stressed, a breaking vowel can occur. This process existed in old French, the stressed Latin vowels had been broken (see: https://halshs.archives-ouvertes.fr/halshs-00365006/PDF/vaissiere_1996_from_latin_to_modern_French.pdf)

The last phenomenon corresponds to the assimilation or coalescence. When two sounds are adjacent, in this case a vowel next to a consonant or vowel, and where one takes a feature from the other, that leads to a diphthongization. Hausa is a language where this kind of assimilation have been observed (see: https://scholarworks.iu.edu/dspace/bitstream/handle/2022/21060/HausaDiphthongs.pdf?sequence=1)

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    And there are also diphthongs that emerge when a consonant is vocalized. Dec 29, 2018 at 14:39
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    Yes, it is the case in Riffian, where the tap [ɾ] is vocalized as an open vowel. So a sequence "ir" or "ur" is carried out as diphthong.
    – amegnunsen
    Dec 29, 2018 at 14:52
  • That also applies to German /r/. Dec 29, 2018 at 15:27
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    @X30Marco that's why I think this answer is not completely to the point of the question. "Diphthongs are not limited to Germanic languages" True, but the West Germanic languages tend to have the same chain shift of the long vowels and it is usually argued that it happened independently. If it is really true that it happened independently then there has to be a shared feature in these languages that caused the chain shift. Dec 29, 2018 at 15:30
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    [something to add to my own statement: the sound changes are not completely the same, but they affected the same (kind of) vowels and had the same effect. In German and Dutch dialects that still had the diphthongs ie, uo, üö the diphthongization can't be the result of a push chain] :) Dec 29, 2018 at 15:42

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