Phonological history of French

Table of vowel outcomes

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: . 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 usually appeared before the palatal consonant, producing a diphthong, which subsequently evolved in complex ways. There were various palatal sources: Classical Latin (e.g. peior "worse"); any consonant followed by a coming from Latin short or in hiatus (e.g. balneum "bath", palātium "palace"); or followed by or (e.g. pācem "peace", cōgitō "I think"); or followed by and preceded by , or (e.g. plāga "wound"); or after a vowel in various sequences, such as (e.g. noctem "night", veclum < vetulum "old", nigrum "black").
• Syllables preceded by a palatal consonant. An 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 brought into contact with a following consonant by loss of the intervening vowel: e.g. medietātem > Proto-Romance > Gallo-Romance (loss of unstressed vowels) > Proto-French (palatalization) > Old French > moitié "half".
• Nasal syllables (followed by an or ), 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 or was deleted unless a vowel followed, and the nasal vowels were lowered; but when the or remained, the nasal quality was lost, with no lowering of the vowel. This produced significant alternations, such as masculine fin vs. feminine fine .
• Syllables closed by followed by another consonant. By Old French times, this was "debuccalized" into , 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 "chard" vs. bête (formerly ) "beast" (borrowed from bēstiam). Sometimes the length difference was accompanied by a difference in vowel quality, e.g. mal "bad" vs. mâle "male" (Latin māsculum < ). Phonemic length disappeared from Parisian French by the 18th century, but survived regionally (now especially in Belgian French).
• Syllables closed by followed by another consonant (although the sequence -lla- was not affected). The vocalized to , 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: , as low-mid vowels were raised to . 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 or in a final syllable).
• A "palatal" context is a stressed syllable where the preceding consonant has a palatal quality, causing a yod 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 in aimé "loved" (originally ) occurred in Old French, while loss of in sot "silly" occurred in Middle French (hence its continuing presence in spelling, which tends to reflect later Old French).

^2 Both and occur in modern French, and there are a small number of minimal pairs, e.g. jeune "young" vs. jeûne "fast (abstain from food)". In general, however, only occurs word-finally, before , and usually before , while occurs elsewhere.

^3 However, the sequences from multiple origins regularly dissimilate to (and later ) except after labials and velars (Latin locus → → lieu , but *volet → → → → veut ).

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

1. medietātem (Classical Latin form)
2. (pronunciation c. 1st century BC)
3. (1st century AD: > )
4. (2nd century AD, loss of nasalization)
5. (c. 3rd–6th century AD: loss of vowel quantity, new lengthening under stress, raising of to in unstressed syllables, loss of intertonic ; first lenition of intervocalic obstruents, causing voicing of the second ; the first is preceded by the consonant and so remains voiceless)
6. (c. 3rd–6th century AD: progressive palatalization in clusters of + consonant)
7. (5th–7th century AD: Bartsch's law, changing into after a palatal or palatalized consonant; second lenition of intervocalic stops, changing into between vowels)
8. (7th century AD: loss of final unstressed )
9. (7th century AD: final devoicing)
10. (9th century AD, Early Old French)
11. (12th century AD: loss of dental fricatives)
12. (12th century AD, Later Old French: dissimilation of the diphthong to )
13. (12th-13th century AD, Late Old French: replacement of falling diphthongs with rising diphthongs)
14. (13th century AD)
15. (18th century AD, Classical French and Modern French) ⟨moitié⟩

Chronological history

To Proto-Romance

• Loss of .
• Loss of final (except in monosyllables: Modern French rien < rem).
• > . The preceding vowel was long as a result of compensatory lengthening (already in Classical Latin).
• > in some words (dorsum > Vulgar Latin *dossu > Modern French dos) but not others (ursum > Modern French ours).
• Fusion of the diphthongs ae and oe to and respectively (it is disputed whether the fusion of ae initially produced a short or long vowel, or postdated the neutralization of Latin vowel length). The diphthong was retained.
• Development of Latin and intervocalic to a voiced labial fricative. The original phonetic realization of this sound was probably bilabial (found today in Spanish as an allophone of ), but it eventually became labiodental in French, and so will be transcribed below.
• Introduction of prosthetic short before words beginning with + consonant, which would later become closed with the Italo-Western vowel change (Spanish espina, Modern French épine "thorn, spine" < espine < spīnam).
• Vulgar Latin unstressed vowel loss: Loss of intertonic (unstressed and in an interior syllable) vowels between , and , .
• Final > , > (Spanish cuatro, sobre < quattuor, super).
• Reduction of and in hiatus to , which would eventually be followed by palatalization of the resulting consonant + sequences.
• Affrication of (2nd–3rd centuries AD).
• Gemination of to .

To Proto-Italo-Western Romance

The following sound changes are shared among Italo-Western Romance languages, but must be dated later than Proto-Romance in the strict sense (assuming a tree model of descent), because they are absent from some dialects of Sardinian. (The merger of Latin to is also generally absent from Eastern/Balkan Romance.)

• Reduction of ten-vowel system to the seven vowels (see table). In unstressed syllables, become , resulting in only five distinct unstressed vowels.
• Palatalization of , before the front vowels (around the fifth century AD). For simplicity, the outcomes can be transcribed as , ; the steps involved in their subsequent phonetic development are debated.

To Old Gallo-Romance, c. 600

• Further changes involving palatalized sounds:
  • and merge as an affricate (treated as a single sound). The double version of this affricate, , is the regular outcome of , from earlier , from unstressed Latin or + vowel.
  • , , , have all merged as by this point. (A merge of some or all of these sounds is also widely seen in other Romance languages, but some languages show divergent developments in at least some words, particularly for .)
  • and become .
  • and become . The intermediate steps are disputed.
  • > and > ; first going through and , respectively.
• First lenition (did not happen in a small area around the Pyrenees): chain shift involving intervocalic singleton consonants. Voiced stops and unvoiced fricatives become voiced fricatives, while unvoiced stops become voiced stops. Specifically, intervocalic > (Latin intervocalic had already become ); intervocalic > , and intervocalic > . The dating is debated; it is sometimes placed as early as the 3rd century AD, but was probably not completed until later; it seems to have been complete in Gaul by the end of the sixth century. Consonants before are lenited, also, and > . Final and are lenited when preceded by a vowel.
  • *malefatius > Early Old French .
• First unstressed vowel loss: Loss of intertonic (unstressed and in an interior syllable) vowels except when pretonic. That occurred at the same time as the first lenition, and individual words inconsistently show one change before the other. Hence manica > manche but grānica > grange. carricāre becomes either charchier or chargier in Old French. However, in some analyses, the standard for central French was initially for lenition to occur before the unstressed vowel loss, and patterns of the order being reversed, resulting in voiceless consonants, were loaned from the more Frankish-influenced Northern dialects of Normandy, Champagne and Lorrain, eventually spreading to some other words by analogy, leading to known cases of divergent development, such as grange and granche, and venger and (re)vencher (the latter both from Latin vindicāre).
• Vowels and are raised to and , when preceding a syllable containing or : illī > il, mōvī > mui, dēbuī > > dui (see also metaphony). The traces of this process were later deleted in the nominative plurals, due to analogy.

To Early Old French, c. 840

Evidence of 9th century French phonology is relatively limited, being based largely on two short documents, the Oaths of Strasbourg, written in 842 in what was likely a deliberately Latinized, archaic form of Romance, and the Sequence of Saint Eulalia, written around 880 in some Romance vernacular of north central France, not directly ancestral to modern French (the modern French form chose requires palatalization of to have taken place before monophthongization of , whereas the Sequence's "cose" shows only the latter of these two sound changes, as in modern Picard). Nevertheless, the following sound changes may be identified as having taken place before or around this period:

• Diphthongization of open-mid vowels in stressed open syllables (where the vowels had likely been allophonically lengthened to ), and also in stressed closed syllables if followed by a palatal sound (often later absorbed). They remain unchanged in other kinds of closed syllables, hence semper > sempre (Eulalia line 10) and mort(u)a > morte (Eulalia line 18). Unstressed did not exist, having merged with . The diphthongs resulting from this sound change are variously transcribed by modern linguists as or . Old French assonances and rhymes suggest that diphthongization initially produces falling diphthongs such as or , with later evolving into a rising diphthong () and later evolving into a front rounded vowel (possibly with or as intermediate steps). However, Porter 1960 reconstructs the rising diphthongs as occurring already in Eulalia.
  • In stressed open syllables: Latin bona, caelum > Early Old French buona, ciel (Eulalia lines 1, 6)
  • Followed by a palatal in stressed closed syllables: peior >> > >> pire "worst"; noctem > > >> nuit; but tertium > >> tierz.
  • Diphthongization in the contexts described above predates the earliest Old French texts, but the exact date of this sound change for northern Gallo-Romance languages is uncertain. Although diphthongization of is a widespread sound change in Romance languages (suggesting it arose relatively early, possibly within a shared community of Late Latin speakers) the conditions in which it occurs are not uniform between languages: for example, diphthongize in both closed and open stressed syllables in Romanian and Spanish, and nowhere in Portuguese. Some linguists date diphthongization to the 6th or 7th century, while others argue it occurred as early as the 3rd or 4th century; Loporcaro (2015) argues the early dating has not been established. Diphthongization affects the vowels in some loanwords from Germanic, such as Germanic *medu > Old French mied, mies "mead".
• Second lenition of intervocalic voiced stops (not in all Gallo-Romance):
  • Between vowels, singleton (from Latin ) become . As before, intervocalic are also affected: patrem, capra, sacrāmentum > > EOF > French père, chèvre, serment. Cf. soure 'over' (Eulalia, line 12). The labialized velar (from Latin between vowels) becomes after stressed front vowels, as in sequit > * > siut, or with metathesis, suit. This can be strengthened to when followed by a vowel or by , as in sequere > * > sivre~siure . Northern and eastern dialects show rather than in this context, hence sequere, sequit > seure~sieure, seut~sieut.
  • This lenition does not affect that had come into contact with a preceding consonant via intertonic vowel loss, even in cases where that preceding consonant eventually becomes lost or vocalized, as in adcubitāre > French accouder, *subitānum > French soudain, *placitāre > French plaider, adjūtāre > French aider. (Pope 1952 interprets forms such as OF aidier, sodain, bondir as showing voicing of to by progressive assimilation after .)
    • In contrast, the glide that develops from diphthongization of (see below) does not protect a following consonant, as seen in monēta > > > Old French moneie, monoie.
• Palatalization of velars before :
  • before become palatal affricates (late fifth to early sixth century). Very few words fail to palatalize: cavea >> cage, not **chage.
  • before becomes a palatal glide when preceded by an unrounded vowel.
    • also becomes a palatal glide in the suffixes -īcum and -(i)ācum (amīcum > ami, Tornācum > Tournai, but not in the words caecum > cieu and graecum > grieu).
• and become ; and become ; becomes . This development was also seen in Occitan and Ligurian.
• When not preceded by a vowel, becomes . The ultimate source can be Late Latin , , , or word-initial :
  • diurnum > EOF jorn , Georgius > OF Georges, argentum > OF argent , iacet > OF gist .
• Where intertonic vowel loss had brought into contact with following , it palatalized them to (as indicated by the development of a following in a stressed originally open syllable). The preceding vowel develops to a diphthong ending in the glide . Examples:
  • impeiorāre > > > > OF empoirier "to worsen" (compare peior > > > pire)
  • medietātem > > > > > moitié
• The glide develops between a vowel and a following palatalized consonant in some cases:
  • Before double (from , , , or ). This will ultimately develop to (spelled "iss"), merging with original .
    • messiōnem > meisson, pisciōnem > peisson, nāscentem > naissant
  • Before single or (from intervocalic , , ). This will ultimately develop to (spelled "is").
    • mānsiōnem > maison, ratiōnem > raison, placēre > plaisir
  • Before (which ultimately develops to , spelled "ir") and also before certain clusters ending in :
    • corium > cuir, ostrea > uistre
  • Before syllable-final . This will ultimately develop to (spelled "in"): ivngit > * > > joint
• But a glide typically does not develop between a vowel and the following consonants:
  • , (which are possibly double , in intervocalic position)
  • (which is possibly double in intervocalic position)
    • faciat > > OF face. (This word occurs in the Oaths of Strasbourg with the spelling ⟨fazet⟩, which is transcribed as by Rickard (2003:22) and Alkire & Rosen (2010:325).)
  • double , which develops to Old French (as in OF doze, treze, seze, from , , )
  • (although in writing was represented by "il" or "ill").
• Morphemic in inherited words becomes instead of , hence operārium > > (not ) >> ouvrier "worker", but ārea >> aire "area" did not participate.
• Diphthongization of and fronting of in stressed, originally open syllables. In other words, these changes affect long , which were either allophones of (if it is assumed that diphthongization preceded degemination and final vowel apocope) or distinct phonemes (if degemination and final vowel apocope preceded diphthongization). There is disagreement about the relative ordering of these sound changes. Diphthongization does not affect vowels followed by a palatal glide or palatalized sound. This diphthongization has been dated to the fourth century, seventh century, or mid-eighth century; it did not occur in all Gallo-Romance.
  • becomes , as in *bellātiōrem > bellezour (Eulalia line 2).
  • becomes when not preceded by a palatal sound, as in concrēdere > concreidre (Eulalia line 21).
    • After a palatal or palatalized consonant, evolves instead to (likely via simplification of ; see below). Examples: cēra > OF cire, pagēnsem > OF païs, placēre > OF plaisir, iacēre > OF gesir
  • , when not followed by a nasal or preceded by a palatal sound, becomes a vowel that can be transcribed as . Its actual phonetic quality is debated: in Early Old French, it is usually written ⟨e⟩ but does not assonate with either or . It evolves later in French to in a closed syllable, in an open one. A diphthong such as may have been a stage in its development, but alternatively it may have simply developed by fronting of to , resulting in a phonemic distinction between the four vowel qualities , , and . Another common interpretation supposes that evolved to or , a distinctively long vowel in contrast to short and , although this would be the only phonemic length contrast in the Early Old French vowel system.
    • Before a nasal, evolves instead to when not preceded by a palatalized consonant: manum, amat > OF main, aime
    • After a palatalized consonant (including the affricates as well as ), evolves instead to . This is known as Bartsch's law, and can be dated to the sixth or seventh century. Examples: *cugitāre > > > > >> OF cuidier "to think", mansiōnātam > > > > OF maisniée "household".
• Other vowel changes:
  • > (sixth or seventh century). (This shift, along with the later > , is an areal feature common to most Gallo-Romance languages.)
  • > . This takes place after the palatalization of velars before .
  • , from Proto-Italo-Western Romance * before a palatal glide, are simplified to (eighth century). (Alternatively, Pope 1952 explains the development of the second as > > > .)
    • lectum > * > lit, noctem > * > nuit, peior > * > pire
    • Compare the development of to when preceded by a palatal or palatalized consonant, described above.
  • Similarly, becomes when preceded by a palatal consonant: iacet > OF gist , cacat > OF chie .
  • Second unstressed vowel loss (complete by around 700 AD):
    • In unstressed final syllables, all vowels except are lost, unless this loss would result in an impermissible final cluster. In that case, the vowel is retained as : mortem > mort, but vincere > veintre (Eualia).
    • Unstressed becomes in final syllables and in open word-medial syllables.
• Other consonant changes:
  • (one of the first consonants lost from Classical Latin) is reintroduced in borrowings from Germanic languages.
  • Single intervocalic is eventually deaffricated to , upon which it merges with the outcome of . There is conflicting evidence of the date of this sound change. The consonant derived from Latin before a front vowel seems to have still been a palatalized affricate or when the following vowel was lost in a final syllable, resulting in word-final in Early Old French (spelled "iz"), later simplified to . In contrast, the consonant derived from Latin + yod seems to have become a palatalized fricative by the time the following vowel was lost in a final syllable, resulting in word-final in Early Old French. In the Sequence of Saint Eulalia, the letter ⟨z⟩ may represent in the words "domnizelle" and "bellezour" (from Latin *domnicella and *bellatiorem).
    • picem > EOF peiz, nucem > EOF noiz, crucem > EOF croiz, pacem > EOF paiz, vocem > EOF voiz
    • palatium > EOF palais, pretium > EOF pris
  • Degemination of obstruents: At some point after the lenition of single intervocalic to , geminate obstruents are simplified to single consonants. This change is variously dated from the 7th-9th century. Since diphthongization of , diphthongization of and fronting of (discussed above) occur only in originally open syllables, some analysts assume that degemination must postdate all of these sound changes. However, it is possible that the distinction at the time of these sound changes was not in the length of the consonant, but in the length of the vowel.
  • Intervocalic (probably still pronounced as bilabial ) is lost when followed, or sometimes when preceded by a rounded vowel:
    • *nūba > > French nue, *habūtum > > French eu, *bibūtum > > French bu
  • is lost in contexts where it did not evolve to ; namely, when either the preceding or the following vowel was rounded:
    • locāre > > French louer, rūga > French rue
  • Obstruents are devoiced when final or when followed by a voiceless obstruent, including after vowel loss.
  • is affricated to after palatal or (dolēs > duels "you hurt" but colligis > * > cuelz, cueuz "you gather"; iungis > * > joinz "you join"; fīlius > filz "son": ⟨z⟩ in such words represents ).
  • Palatal is depalatalized to when not followed by a vowel (ie. when final or followed by a consonant).
    • In first-person verb forms, it may remain palatal when final because of the influence of the palatalized subjunctives.
    • > when depalatalisinɡ (cuneum > > coin, balneum > > bain but montāneam > > montagne.)
  • Palatal is depalatalized to when followed by a consonant, but not when word-final (oculus > ueilz > ).

To Old French, c. 1100

• Loss of , , before final , . (dēbet > Strasbourg Oaths dift > OF doit.)
• Loss of and . When it results in a hiatus of with a following vowel, the becomes a schwa .
• Word-final , > (diurnum > EOF jorn > OF jor; vermem > EOF verm > OF ver; dormit > OF dort).
• Deletion or vocalization of (> ) before consonants:
  • is simply deleted after (filz > fiz ).
  • is also deleted after rounded vowels , , and (multum > > molt~mult ).
  • becomes after the remaining vowels (alterum > > autre ).
    • However, (< in open syllables) and when affected by this process, become the sequences and , respectively (pālus > > pieus , and bellus > > beaus ).
• > (blocked by nasalization; see below).
• > , however this is blocked if a labial consonant follows, in which case the segment remains , ultimately becoming later. (lupa > OF louve.)
• > (blocked by nasalization; see below).
• > > after labials and velars, but elsewhere (Latin locus → → lieu , but *volet → → → → veut ).
• develops allophone before , which later develops into a separate phoneme.
• Loss of before voiced consonant (passing first through ), with lengthening of preceding vowel. That produces a new set of long vowel phonemes, as is described more completely in the following section.

To Late Old French, c. 1250–1300

Changes here affect oral and nasal vowels alike, unless otherwise indicated.

To Middle French, c. 1500

Changes here affect oral and nasal vowels alike, unless otherwise indicated.

• ⟨ei⟩ > (the diphthong is maintained in Quebec French: neige "snow" or ).
• Loss of final consonants before a word beginning with a consonant. That produces a three-way pronunciation for many words (alone, followed by a vowel, followed by a consonant), which is still maintained in the words six "six" and dix "ten" (and until recently neuf "nine"), e.g. dix "ten" but dix amis "ten friends" and dix femmes "ten women".
• Subject pronouns start to become mandatory because of loss of phonetic differences between inflections.
• Medieval apical s, as in saint, merges into deaffricated ⟨c⟩ as in ceint, thus merging soft ⟨c⟩ and ⟨s⟩.

To Early Modern French, c. 1700

• ⟨au⟩ > > in Late Middle French (around the 16th century).
• ⟨eau⟩ > > in Later Middle French > (from around the end of the 16th century to the mid-17th century).
• Loss of most phonemically lengthened vowels (preserved in Belgian, Acadian French and Quebec French).
• Loss of final consonants in a word standing alone. That produces a two-way pronunciation for many words (in close connection with a following word that begins with a vowel), often still maintained: nous voyons "we see" vs. nous avons "we have". That phenomenon is known as liaison.
• ⟨oi⟩ > (see above – To Late Old French) or (étoit > était; the spelling was not changed until the 19th century). This also affects certain other instances of ; e.g. moelle , poêle .
  • Change into is relatively rare in standard French, it occurs notably in the imperfect tense suffixes (-ais, -ait, and -aient), the adjectival suffix -ois > -ais, as well as other few words, e.g. connoître > connaître.
  • The pronunciation is preserved in some forms of Quebec and Acadian French, especially by old speakers.
• Instances of were again deleted in the late seventeenth century. The phoneme had been reintroduced to the language through the absorption of loanwords, primarily of Germanic origin, and these are the instances that were lost this time around. However a Germanic ⟨h⟩ usually disallows liaison: les halles , les haies , les haltes , whereas a Latin ⟨h⟩ allows liaison: les herbes , les hôtels .

To Modern French, c. 2000

• becomes a uvular sound ("Guttural R"), realized as either a trill or fricative , in most accents. The alveolar trill is maintained in Acadia, Louisiana, some parts of Québec and in Francophone Africa.
• Merger of (spelled ⟨il⟩ in œil and travail) into , which had begun in the seventeenth and eighteenth centuries, reaches completion around the beginning of the nineteenth century (see Mouillé)
• Elision of final , and occasionally of elsewhere, unless a sequence of three consonants would be produced (such constraints operate over multiword sequences of words that are syntactically connected). Occitan French tends to be more conservative, while the elision of final does not occur in Francophone Africa.
• Changing use of liaison, which overall becomes rarer.
• In Metropolitan French, gradual merging of and , both are realized as , but the distinction is maintained in Southern France, Switzerland, Belgium, Quebec and Francophone Africa.
• In Metropolitan French, loss of the phoneme , merged with , both are realized as , but the distinction is maintained in French Switzerland, Belgium, Quebec and Francophone Africa.
• In Metropolitan French, loss of the phoneme , merged with , both are realized as , but the distinction is maintained in Quebec French.
• In Metropolitan French, loss of the phoneme , merged with , both are realized as , but the distinction is maintained in Northern French, Switzerland, Belgium, Quebec and Francophone Africa.
• In Metropolitan French, merger of into when word-final, but the distinction is maintained in Belgian French.

Loss of final consonants

The loss (apocopation) of final consonants does not just affect French and all other langues d'oïl, but also some dialects of Franco-Provençal and Occitan. This process began in the late 12th century CE, and this might have to do with the variable pronunciation of final consonants.

• The first known consonant to be affected was and it occurred before consonants. Prior to this, and were voiced to and before words starting in a vowel.
• Final consonants outside of consonant clusters could be retained before a word starting in vowel, at pause, or in monosyllabic words (sec vs. cerf ).
• could vocalize or delete in word-final position, but this process is unpredictable, due to later analogy and restoration of this consonant.
  • usually does not change after low and mid vowels, except through analogy with the respective plural forms. (caballus > cheval instead of stereotypical chevau, but capillus > chevel > cheveu based on its plural cheveus).
  • tends to be unpronounced after high vowels as of 13th century, however, most words have restored this consonant in Classical French (fil > , but cul remains as such).

Nasalization

Nasalization of vowels before or 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 , , before or (originally, in all circumstances, including when a vowel followed).
• Nasalization occurs before and blocks the changes > and > . However, the sequence occurs because has more than one origin: coin "corner" < cvnevm. The sequences or , and or , 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 and to but not in the sequences and : bien, plein. The realization of to probably occurred during the 11th or early 12th century and did not affect Old Norman or Anglo-Norman. Ultimately merged into .
• Nasalization of , , before or .
• It is not clear if the third-person plural ending -ent contained a nasalized schwa ; although the n is consistently kept in writing, by Early Modern French at the latest it had become non-nasal .

The following steps occurred during the Middle French period:

• Lowering of > > . ( usually comes from original , as original became .)
• Denasalization of vowels before or followed by a vowel or semi-vowel. (Examples like femme "woman" < OF < fēminam and donne "(he) gives" < OF < 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 or after remaining nasal vowels (when preceding a consonant or word-final): dent "tooth" < < OFr dent < EOFr < dentem.

The following steps occurred during the Modern French period:

• > > > ( in Quebec French). That also affects diphthongs such as > > (bien "well" < bene); > > , (juin "June" < iūnium); > > , (coin "corner" < cuneum). Also, > , (pain "bread" < pānem); > , (plein "full" < plēnum).
• > > , but the sound is maintained in Quebec French.
• > ( in Quebec French)
• > > ( in Quebec French). In the 20th century, this sound has low functional load and has tended to merge with .

That leaves only four nasal vowels: , , , and , the last often no longer being distinguished from the first.