Phonological history of French

A profound change in very late spoken Latin (Vulgar Latin, the forerunner of all the Romance languages) was the restructuring of the vowel system of Classical Latin. Latin had thirteen distinct vowels: ten pure vowels (long and short versions of a, e, i, o, u), and three diphthongs (ae, oe, au).[2] What happened to Vulgar Latin is set forth in the table.[3]

Essentially, the ten pure vowels were reduced to the seven vowels /a ɛ e i ɔ o u/, and vowel length was no longer a distinguishing feature. The diphthongs ae and oe fell in with /ɛ/ and /e/, respectively. Au was retained, but various languages (including Old French) eventually turned it into /ɔ/ after the original /ɔ/ fell victim to further changes.

The complex but regular French sound changes have caused irregularities in the conjugation of Old French verbs, like stressed stems caused by historic diphthongization (amer, aim, aimes, aime, aiment, but amons, amez), or regular loss of certain phonemes (vivre, vif, vis, vit). Later in Modern French, these changes were limited to fewer irregular verbs. Modern French also had lost the class of rather unpredictable -ier verbs (resulting from ejection of /j/ into the infinitive suffix -āre, which still exists in some langues d'oïl), having been replaced by simple -er verbs plus -i instead, as in manier, but Old French laissier → laisser.

Vowel length became automatically determined by syllable structure, with stressed open syllables having long vowels and other syllables having short vowels. Furthermore, the stress on accented syllables became more pronounced in Vulgar Latin than in Classical Latin. That tended to cause unaccented syllables to become less distinct, while working further changes on the sounds of the accented syllables. That especially applied to the new long vowels, many of which broke into diphthongs but with different results in each daughter language.

Old French underwent more thorough alterations of its sound system than did the other Romance languages. Vowel breaking is observed to some extent in Spanish and Italian: Vulgar Latin focu(s) "fire" (in Classical Latin, "hearth") becomes Italian fuoco and Spanish fuego. In Old French, it went even further than in any other Romance language; of the seven vowels inherited from Vulgar Latin, only /i/ remained unchanged in stressed open syllables:

• The sound of Latin short e, turning to /ɛ/ in Proto-Romance, became ie in Old French: Latin mel, "honey" > OF miel
• The sound of Latin short o > Proto-Romance /ɔ/ > OF uo, later ue: cor > cuor > cuer, "heart"
• Latin long ē and short i > Proto-Romance /e/ > OF ei: habēre > aveir, "to have"; this later becomes /oi/ in many words, as in avoir
• Latin long ō and short u > Proto-Romance /o/ > OF ou, later eu: flōrem > flour, "flower"
• Latin a, ā > Proto-Romance /a/ > OF /e/, probably through an intervening stage of /æ/; mare > mer, "sea". That change also characterizes the Gallo-Italic languages of Northern Italy (cf. Bolognese [mɛːr]).

Furthermore, all instances of Latin long ū > Proto-Romance /u/ became /y/, the lip-rounded sound that is written u in Modern French. That occurred in both stressed and unstressed syllables, regardless of whether open or closed.

Latin au did not share the fate of /ɔ/ or /o/; Latin aurum > OF or, "gold": not *œur nor *our. Latin au must have been retained at the time such changes were affecting Proto-Romance.

Changes affecting consonants were also quite pervasive in Old French. Old French shared with the rest of the Vulgar Latin world the loss of final -M. Old French also dropped many internal consonants when they followed the strongly stressed syllable; Latin petram > Proto-Romance */ˈpɛðra/ > OF pierre; cf. Spanish piedra ("stone").

In some contexts, /oi/ became /e/, still written oi in Modern French. During the early Old French period, it was pronounced as the writing suggests, as /oi/ as a falling diphthong: /oi̯/. It later shifted to become rising, /o̯i/, before becoming /o̯e/. The sound developed variously in different varieties of Oïl: most of the surviving languages maintain a pronunciation as /we/, but Literary French adopted a dialectal pronunciation, /wa/. The doublet of français and François in modern French orthography demonstrates the mix of dialectal features.

At some point during the Old French period, vowels with a following nasal consonant began to be nasalized. While the process of losing the final nasal consonant took place after the Old French period, the nasal vowels that characterize Modern French appeared during the period in question.

The following table shows the most important modern outcomes of Vulgar Latin vowels, starting from the seven-vowel system of Proto-Western Romance stressed syllables: /a/, /ɛ/, /e/, /i/, /ɔ/, /o/, /u/. The vowels developed differently in different contexts, with the most important contexts being:

• "Open" syllables (followed by at most one consonant), where most of the vowels were diphthongized or otherwise modified.
• Syllables followed by a palatal consonant. An /i/ usually appeared before the palatal consonant, producing a diphthong, which subsequently evolved in complex ways. There were various palatal sources: Classical Latin /jj/ (e.g. peior[4] "worse"); any consonant followed by a /j/ coming from Latin short /e/ or /i/ in hiatus (e.g. balneum "bath", palātium "palace"); /k/ or /ɡ/ followed by /e/ or /i/ (e.g. pācem "peace", cōgitō "I think"); /k/ or /ɡ/ followed by /a/ and preceded by /a/, /e/ or /i/ (e.g. plāga "wound"); /k/ or /ɡ/ after a vowel in various sequences, such as /kl/, /kr/, /ks/, /kt/, /ɡl/, /ɡn/, /ɡr/ (e.g. noctem "night", veclum < vetulum "old", nigrum "black").
• Syllables preceded by a palatal consonant. An /i/ appeared after the palatal consonant, producing a rising diphthong. The palatal consonant could arise in any of the ways just described. In addition, it could stem from an earlier /j/ brought into contact with a following consonant by loss of the intervening vowel: e.g. medietātem > Proto-Romance /mejjeˈtate/ > Gallo-Romance /mejˈtat/ (loss of unstressed vowels) > Proto-French /meiˈtʲat/ (palatalization) > Old French /moiˈtjɛ/ > moitié /mwaˈtje/ "half".
• Nasal syllables (followed by an /n/ or /m/), where nasal vowels arose. Nasal syllables inhibited many of the changes that otherwise happened in open syllables; instead, vowels tended to be raised. Subsequently, the following /n/ or /m/ was deleted unless a vowel followed, and the nasal vowels were lowered; but when the /n/ or /m/ remained, the nasal quality was lost, with no lowering of the vowel. This produced significant alternations, such as masculine fin /fɛ̃/ vs. feminine fine /fin/.
• Syllables closed by /s/ followed by another consonant. By Old French times, this /s/ was "debuccalized" into /h/, which was subsequently lost, with a phonemic long vowel taking its place. These long vowels remained for centuries, and continued to be indicated by an s, and later a circumflex, with alternations such as bette /bɛt/ "chard" vs. bête (formerly /bɛːt/) "beast" (borrowed from bēstiam). Sometimes the length difference was accompanied by a difference in vowel quality, e.g. mal /mal/ "bad" vs. mâle /mɑːl/ "male" (Latin māsculum < */ˈmaslə/). Phonemic (although not phonetic) length disappeared from Parisian French by the 18th century, but survived regionally (now especially in Belgian French).
• Syllables closed by /l/ followed by another consonant (although the sequence -lla- was not affected). The /l/ vocalized to /w/, producing a diphthong, which then developed in various ways.
• Syllables where two or more of the above conditions occurred simultaneously, which generally evolved in complex ways. Common examples are syllables followed by both a nasal and a palatal element (e.g. from Latin -neu-, -nea-, -nct-); open syllables preceded by a palatal (e.g. cēram "wax"); syllables both preceded and followed by a palatal (e.g. iacet "it lies"); syllables preceded by a palatal and followed by a nasal (e.g. canem "dog").

The developments in unstressed syllables were both simpler and less predictable. In Proto-Western Romance, there were only five vowels in unstressed syllables: /a/, /e/, /i/, /o/, /u/, as low-mid vowels /ɛ/, /ɔ/ were raised to /e/, /o/. These syllables were not subject to diphthongization and many of the other complex changes that affected stressed syllables. This produced many lexical and grammatical alternations between stressed and unstressed syllables. However, there was a strong tendency (especially beginning in the Middle French period, when the formerly strong stress accent was drastically weakened) to even out these alternations. In certain cases in verbal paradigms an unstressed variant was imported into stressed syllables, but mostly it was the other way around, with the result that in Modern French all of the numerous vowels can appear in unstressed syllables.

^1 "Context" refers to the syllable context at the Vulgar Latin or Gallo-Romance stage. The contexts are as follows:

• An "open" context is a stressed syllable followed by at most a single consonant at the Vulgar Latin stage.
• A "closed" context is any other syllable type (unstressed, or followed by two or more consonants).
• A "late closed" context is a context that is open at the Vulgar Latin (Proto-Romance) stage but becomes closed in the Gallo-Romance stage due to loss an unstressed vowel (usually /e/ or /o/ in a final syllable).
• A "palatal" context is a stressed syllable where the preceding consonant has a palatal quality, causing a yod /j/ to be generated after the preceding consonant, before the stressed vowel.

Changes that occurred due to contexts that developed during the Old French stage or later are indicated in the "Modern French" column. In particular, "+#" indicates a word-final context in modern French, which generally evolved due to loss of a final consonant in Old French or Middle French. For example, loss of /θ/ in aimé "loved" (originally /aiˈmɛθ/) occurred in Old French, while loss of /t/ in sot "silly" occurred in Middle French (hence its continuing presence in spelling, which tends to reflect later Old French).

^2 Both /œ/ and /ø/ occur in modern French, and there are a small number of minimal pairs, e.g. jeune /ʒœn(ə)/ "young" vs. jeûne /ʒøn(ə)/ [ʒøːn(ə)] "fast (abstain from food)". In general, however, /ø/ only occurs word-finally, before /z/, and usually before /t/, while /œ/ occurs elsewhere.

^3 However, the sequences */wɛw/ from multiple origins regularly dissimilate to /jɛw/ (and later /jœ/, /jø/) except after labials and velars (Latin locus → /lwɛw/ → lieu /ljø/, but *volet → /vwɛwθ/ → veut /vø/).[7]

^4 The changes producing French moitié /mwaˈtje/ were approximately as follows:

1. medietātem (Classical/Late Latin form)
2. /medjeˈtaːtẽː/ (pronunciation c. 1 AD)
3. /mejjeˈtate/ (Proto-Romance form, with /dj/ > /jj/ and loss of vowel length)
4. /mejˈtate/ (loss of intertonic /e/)
5. /mejˈtʲate/ (late palatalization of /t/ by preceding /j/)
6. /mejˈtʲade/ (first lenition of second /t/, but first one protected by preceding consonant /j/)
7. /mejˈtʲaːde/ (lengthening of stressed vowel in open syllable)
8. /mejˈtʲaːd/ (Gallo-Romance loss of final unstressed /e/)
9. /mejˈtʲaːð/ (second lenition)
10. /mejˈtʲaːθ/ (final devoicing)
11. /mejˈtiæθ/ (Proto-French changes in "palatal + open" context, with the long /aː/ reflecting the former open-syllable context)
12. /meiˈtiɛθ/ (Early Old French vowel changes)
13. /moiˈtjɛ/ (Late Old French changes: /ei/ > /oi/, /iɛ/ > /jɛ/, loss of /θ/)
14. /mweˈtje/ (Changes to Middle French: /oi/ > /we/, final /ɛ/ > /e/)
15. /mwaˈtje/ (Changes to modern French: /we/ > /wa/)

Nasalization of vowels before /n/ or /m/ occurred gradually over several hundred years, beginning with the low vowels, possibly as early as 900, and finishing with the high vowels, possibly as late as c. 1300. Numerous changes occurred afterwards that are still continuing.

The following steps occurred during the Old French period:

• Nasalization of /a/, /e/, /ɔ/ before /n/ or /m/ (originally, in all circumstances, including when a vowel followed).
• Nasalization occurs before and blocks the changes /ei/ > /oi/ and /ou/ > /eu/. However, the sequence /õĩ/ occurs because /oi/ has more than one origin: coin "corner" < cvnevm. The sequences /ĩẽn/ or /ĩẽm/, and /ũẽn/ or /ũẽm/, also occur, but the last two occur in only a few words, in each case alternating with a non-diphthongized variant: om or uem (ModF on), and bon or buen (ModF bon). The version without the diphthong apparently arose in unstressed environments and is the only one that survived.
• Lowering of /ẽ/ and /ɛ̃/ to [æ̃] but not in the sequences /jẽ/ and /ẽj/: bien, plein. The realization of /ẽ/ to [æ̃] probably occurred during the 11th or early 12th century and did not affect Old Norman or Anglo-Norman. Ultimately [æ̃] merged into /ã/.
• Nasalization of /i/, /u/, /y/ before /n/ or /m/.
• It is not clear if the third-person plural ending -ent contained a nasalized schwa /ə̃/; although the n is consistently kept in writing, by Early Modern French at the latest it had become non-nasal /ə/.

The following steps occurred during the Middle French period:

• Lowering of /ũ/ > /õ/ > /ɔ̃/. (/ũ/ usually comes from original /oN/, as original /u/ became /y/.)
• Denasalization of vowels before /n/ or /m/ followed by a vowel or semi-vowel. (Examples like femme /fam/ "woman" < OF /ˈfãmə/ < fēminam and donne /dɔn/ "(he) gives" < OF /ˈdũnə/ < dōnat, with lowering and lack of diphthongization before a nasal even when a vowel followed, show that nasalization originally operated in all environments.)
• Deletion of /n/ or /m/ after remaining nasal vowels (when preceding a consonant or word-final): dent /dɑ̃/ "tooth" < */dãt/ < OFr dent /dãnt/ < EOFr */dɛ̃nt/ < dentem.

The following steps occurred during the Modern French period:

• /ĩ/ > /ẽ/ > /ɛ̃/ > [æ̃] ([ẽɪ̯̃] in Quebec French). That also affects diphthongs such as /ĩẽ/ > /jẽ/ > /jɛ̃/ (bien /bjɛ̃/ "well" < bene); /ỹĩ/ > /ɥĩ/ > /ɥɛ̃/, (juin /ʒɥɛ̃/ "June" < iūnium); /õĩ/ > /wẽ/ > /wɛ̃/, (coin /kwɛ̃/ "corner" < cuneum). Also, /ãĩ/ > /ɛ̃/, (pain /pɛ̃/ "bread" < pānem); /ẽĩ/ > /ɛ̃/, (plein /plɛ̃/ "full" < plēnum).
• /ã/ > /ɑ̃/ > [ɒ̃], but the [ã] sound is maintained in Quebec French.
• /ɔ̃/ > [õ] ([õʊ̯̃] in Quebec French)
• /ỹ/ > /œ̃/ ([ɚ̃] in Quebec French). In the 20th century, this sound has low functional load and has tended to merge with /ɛ̃/.

That leaves only four nasal vowels: /ɛ̃/, /ɑ̃/, /ɔ̃/, and /œ̃/, the last often no longer being distinguished from the first.

• Bartsch's law
• History of French § Internal phonological history

• Boyd-Bowman, Peter (1980), From Latin to Romance in Sound Charts, Georgetown University Press, ISBN 978-0878400775
• Brittain, Margaret S. (1900). Historical Primer of French Phonetics and Inflection. Oxford: Clarendon Press.
• Gess, Randall (1996) Optimality Theory in the Historical Phonology of French. PhD dissertation, University of Washington
• Harris, Martin (1988), "French", in Harris, Martin; Vincent, Nigel (eds.), The Romance Languages, Oxford University Press, pp. 209–245, ISBN 978-0195208290
• Kibler, William (1984), Introduction to Old French, Modern Language Association of America, ISBN 978-0873522922
• Price, Glanville (1971), French Language: Present and Past, Jameson Books, ISBN 978-0844800356