In historical linguistics, vowel breaking, vowel fracture,[1] or diphthongization is the sound change of a monophthong into a diphthong or triphthong.


Vowel breaking may be unconditioned or conditioned. It may be triggered by the presence of another sound, by stress, or in no particular way.


Vowel breaking is sometimes defined as a subtype of diphthongization, when it refers to harmonic (assimilatory) process that involves diphthongization triggered by a following vowel or consonant.

The original pure vowel typically breaks into two segments. The first segment matches the original vowel, and the second segment is harmonic with the nature of the triggering vowel or consonant. For example, the second segment may be /u/ (a back vowel) if the following vowel or consonant is back (such as velar or pharyngeal), and the second segment may be /i/ (a front vowel) if the following vowel or consonant is front (such as palatal).

Thus, vowel breaking, in the restricted sense, can be viewed as an example of assimilation of a vowel to a following vowel or consonant.


Vowel breaking is sometimes not assimilatory and is then not triggered by a neighboring sound. That was the case with the Great Vowel Shift in English in which all cases of /iː/ and /uː/ changed to diphthongs.


Vowel breaking sometimes occurs only in stressed syllables. For instance, Vulgar Latin open-mid /ɛ/ and /ɔ/ changed to diphthongs only when they were stressed.

Indo-European languages


Vowel breaking is a very common sound change in the history of the English language, occurring at least three times (with some varieties adding a fourth) listed here in reverse chronological order:

Southern American English

Main article: Southern American English

Vowel breaking is characteristic of the "Southern drawl" of Southern American English, where the short front vowels have developed a glide up to [j], and then in some areas back down to schwa: pat [pæjət], pet [pɛjət], pit [pɪjət].[2]

Great Vowel Shift

The Great Vowel Shift changed the long vowels /iː uː/ to diphthongs, which became Modern English /aɪ aʊ/.

Middle English

Main article: Middle English phonology § Breaking

In early Middle English, a vowel /i/ was inserted between a front vowel and a following /h/ (pronounced [ç] in this context), and a vowel /u/ was inserted between a back vowel and a following /h/ (pronounced [x] in this context).

That is a prototypical example of the narrow sense of "vowel breaking" as described above: the original vowel breaks into a diphthong that assimilates to the following consonant, gaining a front /i/ before a palatal consonant and /u/ before a velar consonant.

Old English

Main articles: Phonological history of Old English § Breaking and retraction, and Phonological history of Old English § Back mutation

In Old English, two forms of harmonic vowel breaking occurred: breaking and retraction and back mutation.

In prehistoric Old English, breaking and retraction changed stressed short and long front vowels i, e, æ to short and long diphthongs spelled io, eo, ea when followed by h or by r, l + another consonant (short vowels only), and sometimes w (only for certain short vowels):[3]

In late prehistoric Old English, back mutation changed short front i, e, æ to short diphthongs spelled io, eo, ea before a back vowel in the next syllable if the intervening consonant was of a certain nature. The specific nature of the consonants that trigger back umlaut or block it varied from dialect to dialect.

Old Norse

Main article: Old Norse phonological processes

Proto-Germanic stressed short e becomes ja or (before u) regularly in Old Norse except after w, r, l. Examples are:

According to some scholars,[4] the diphthongisation of e is an unconditioned sound change, whereas other scholars speak about epenthesis[5] or umlaut.[6]

German and Yiddish

The long high vowels of Middle High German underwent breaking during the transition to Early New High German: /iː uː//aɪ̯ ɔʏ̯ aʊ̯/. In Yiddish, the diphthongization affected the long mid vowels as well: /ɛː øː uː//ɛɪ̯ ɔɪ̯ ɛɪ̯ aɪ̯ aɪ̯ ɔɪ̯/

This change started as early as the 12th century in Upper Bavarian and reached Moselle Franconian only in the 16th century. It did not affect Alemannic or Ripuarian dialects, which still retain the original long vowels.

In Yiddish, the diphthongization applied not only to MHG long vowels but also to /ɛː oː/ in words of Hebrew (in stressed open syllables) or Slavic origin:

Scottish Gaelic

Vowel breaking is present in Scottish Gaelic with the following changes occurring often but variably between dialects: Archaic Irish → Scottish Gaelic and Archaic Irish → Scottish Gaelic [7] Specifically, central dialects have more vowel breaking than others.

Romance languages

Many Romance languages underwent vowel breaking. The Vulgar Latin open vowels e /ɛ/ and o /ɔ/ in stressed position underwent breaking only in open syllables in French and Italian, but in both open and closed syllables in Spanish. Vowel breaking was mostly absent in Catalan, in which /ɛ/ and /ɔ/ became diphthongs only before a palatal consonant: Latin coxa 'thigh', octō 'eight', lectum 'bed' > Old Catalan */kuoiʃa/, */uoit/, */lieit/. The middle vowel was subsequently lost if a triphthong was produced: Modern Catalan cuixa, vuit, llit (cf. Portuguese coxa, oito, leito). Vowel breaking was completely absent in Portuguese. The result of breaking varies between languages: e and o became ie and ue in Spanish, ie and uo in Italian and ie and eu /ø/ in French.

In the table below, words with breaking are bolded.

Syllable shape Latin Spanish French Italian Portuguese Catalan
Open petram, focum piedra, fuego pierre, feu pietra, fuoco pedra, fogo pedra, foc
Closed festam, portam fiesta, puerta fête, porte festa, porta festa, porta festa, porta


Main articles: History of Romanian § Breaking of stressed open e, and History of Romanian § Breaking of e and o

Romanian underwent the general Romance breaking only with /ɛ/, as it did not have /ɔ/:

It underwent a later breaking of stressed e and o to ea and oa before a mid or open vowel:

Sometimes a word underwent both forms of breaking in succession:

The diphthongs that resulted from the Romance and the Romanian breakings were modified when they occurred after palatalized consonants.

Quebec French

Main article: Quebec French phonology

In Quebec French, long vowels are generally diphthongized when followed by a consonant in the same syllable (even when a final [ʁ] is optionally made silent).


Some scholars[8] believe that Proto-Indo-European (PIE) i, u had vowel-breaking before an original laryngeal in Greek, Armenian and Tocharian but that the other Indo-European languages kept the monophthongs:

However, the hypothesis has not been widely adopted.

Non-Indo-European languages

Austronesian languages

Some languages in Sumatra have vowel breaking processes, almost exclusively in syllable-final position. In Minangkabau, the Proto-Malayic vowels *i and *u are broken to ia and ua before word-final *h, *k, *l, , *r (*təlur > *təluar > talua "egg").[9] In Rejang, the Proto-Malayo-Polynesian vowels , i, and u are broken to êa, ea, and oa before any of word-final consonants above except *k and (*tənur > *tənoar > tênoa "egg").[10] This process has been transphonologized by loss of *l and *r and merging of several word-final consonants into a glottal stop (*p, *t, *k in Minangkabau, or *k, *h in most dialects of Rejang except Kebanagung).

Word-final Proto-Malayo-Polynesian *-i and *-u were also broken in Sumatra. In Rejang, these vowels are broken into -ai and -au in Pesisir dialect, or into -êi and -êu elsewhere.[10]

See also


  1. ^ The American Heritage Dictionary of the English Language, Fourth Edition 2000 by Houghton Mifflin Company.
  2. ^ Kathryn LaBouff, Singing and Communicating in English, Oxford University Press, 2007, p. 268.
  3. ^ Robert B. Howell 1991. Old English breaking and its Germanic analogues (Linguistische Arbeiten, 253.). Tübingen: Max Niemeyer
  4. ^ J. Svensson, Diftongering med palatalt förslag i de nordiska språken, Lund 1944.
  5. ^ H. Paul, "Zur Geschichte des germanischen Vocalismus", Beiträge zur Geschichte der deutschen Sprache und Kultur 6 (1879) 16-30.
  6. ^ K. M. Nielsen, Acta Philologica Scandinavica 24 (1957) 33-45.
  7. ^ Martin John Ball, James Fife (1993). The Celtic Languages. Psychology Press. p. 152. ISBN 9780415010351.
  8. ^ F. Normier, in: Zeitschrift für vergleichende Sprachforschung 91 (1977) 171-218; J.S. Klein, in: Die Laryngaltheorie und die Rekonstruktion des indogermanischen Laut- und Formensystems, Heidelberg 1988, 257-279; Olsen, Birgit Anette, in: Proceedings of the fourth international conference on Armenian linguistics, Cleveland's State University, Cleveland, Ohio, September 14–18, 1991, Delmar (NY) 1992, 129-146; J.E. Rasmussen, in: Selected Papers on Indo-European Linguistics, Copenhagen 1999, 442-458.
  9. ^ Adelaar, K. Alexander (1992). Proto-Malayic: The Reconstruction of its Phonology and Parts of its Lexicon and Morphology. Pacific Linguistics, Series C, no. 119. Canberra: Dept. of Linguistics, Research School of Pacific Studies, The Australian National University. doi:10.15144/PL-C119. hdl:1885/145782. ISBN 978-0-85883-408-8.
  10. ^ a b "Some Irregular Reflexes of Proto-Malayo-Polynesian Vowels in the Rejang Language of Sumatra" (PDF). Archived from the original (PDF) on 2017-08-08.