Phonological history of French

French exhibits perhaps the most extensive phonetic changes (from Latin) of any of the Romance languages. Similar changes are seen in some of the northern Italian regional languages, such as Lombard or Ligurian. Most other Romance languages are significantly more conservative phonetically, with Spanish and especially Italian showing the most conservatism, and Portuguese, Occitan, Catalan and Romanian showing moderate conservatism.

French also shows enormous phonetic changes between the Old French period and the modern language. Spelling, however, has barely changed, which accounts for the wide differences between current spelling and pronunciation. Some of the most profound changes have been:

• The loss of almost all final consonants.
• The subsequent loss of final /ə/, which caused the appearance of many newly final consonants.
• The loss of the formerly strong stress that had characterized the language throughout much of its history and triggered many of the phonetic deformations.
• Significant transformations in the pronunciation of vowels, especially nasal vowels.

Only few of these changes are reflected in the orthography.

Overview

A profound change in very late spoken Latin (i.e. early Common Romance, 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). What happened to Vulgar Latin is set forth in the table. Essentially, the ten pure vowels were reduced to the seven vowels /a ɛ e i ɔ o u/, where vowel length was no longer a distinguishing feature. The diphthongs AE and OE fell in with /ɛ/ and /e/, respectively. AU was retained, but in various languages (including Old French) eventually turned into /ɔ/ after the original /ɔ/ fell victim to further changes.

Development of French pronunciation over time

Form ("to sing")	Latin	Old French		Modern French
		spelling	pronunciation	spelling	pronunciation
Infinitive	cantāre	chanter	/tʃãnˈtæɾ/	chanter	/ʃɑ̃ˈte/
Past Part.	cantātvm	chanté(ṭ)	/tʃãnˈtæ(θ)/	chanté	/ʃɑ̃ˈte/
Gerund	cantandō	chantant	/tʃãnˈtãnt/	chantant	/ʃɑ̃ˈtɑ̃/
1sg. indic.	cantō	chant	/tʃãnt/	chante	/ʃɑ̃t/
2sg. indic.	cantās	chantes	/ˈtʃãntəs/	chantes	/ʃɑ̃t/
3sg. indic.	cantat	chante(ṭ)	/ˈtʃãntə(θ)/	chante	/ʃɑ̃t/
1pl. indic.	cantāmvs	chantons	/tʃãnˈtũns/	chantons	/ʃɑ̃ˈtɔ̃/
2pl. indic.	cantātis	chantez	/tʃãnˈtæts/	chantez	/ʃɑ̃ˈte/
3pl. indic.	cantant	chantent	/ˈtʃãntə(n)t/	chantent	/ʃɑ̃t/
1sg. subj.	cantem	chant	/tʃãnt/	chante	/ʃɑ̃t/
2sg. subj.	cantēs	chanz	/tʃãnts/	chantes	/ʃɑ̃t/
3sg. subj.	cantet	chant	/tʃãnt/	chante	/ʃɑ̃t/
1pl. subj.	cantēmus	chantons	/tʃãnˈtũns/	chantions	/ʃɑ̃ˈtjɔ̃/
2pl. subj.	cantētis	chantez	/tʃãnˈtæts/	chantiez	/ʃɑ̃ˈtje/
3pl. subj.	cantent	chantent	/ˈtʃãntə(n)t/	chantent	/ʃɑ̃t/
2sg. impv.	cantā	chante	/ˈtʃãntə/	chante	/ʃɑ̃t/
2pl. impv.	cantāte	chantez	/tʃãnˈtæts/	chantez	/ʃɑ̃ˈte/

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. This tended to cause unaccented syllables to become less distinct, while working further changes on the sounds of the accented syllables. This especially applied to the new long vowels, many of which broke into diphthongs, although with different results in each of the daughter languages.

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; e.g. Vulgar Latin focv(s) "fire" (in Classical Latin, "hearth") becomes Italian fuoco and Spanish fuego. But in Old French the phenomenon went 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" This change also characterizes the Gallo-Italic dialects 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. This 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 avrvm > OF or, "gold": not *œur nor *our. Latin AU must have been retained at the time these changes were affecting Proto-Romance.

Changes affecting the consonants were also quite pervasive in Old French. Old French shared with the rest of the Vulgar Latin world the loss of final -M. Since this sound was basic to the Latin noun case system, its loss levelled the distinctions upon which the synthetic Latin syntax relied, and forced the Romance languages to adapt a more analytic syntax based on word order. 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").

Table of Old French outcomes of Latin vowels

Letter	Classical Latin	Vulgar Latin	Proto Western Romance	Early Old French (through early 12th c.)		Later Old French (from late 12th c.)
				closed	open	closed	open
Short A	/a/	/a/		⟨a⟩ /a/	⟨e, ie⟩ /æ, iə/	⟨a⟩ /a/	⟨e, ie⟩ /ɛ, jɛ/
Long A	/aː/
AE	/ai/	/ɛ/		⟨e⟩ /ɛ/	⟨ie⟩ /iə/	⟨e⟩ /ɛ/	⟨ie⟩ /jɛ/
Short E	/e/
OE	/oi/	/e/	/e/	⟨e⟩ /e/	⟨ei⟩ /ei/		⟨oi⟩ /oi/ > /wɛ/
Long E	/eː/
Short I	/i/	/ɪ/
Short Y	/y/
Long I	/iː/	/i/		⟨i⟩ /i/
Long Y	/yː/
Short O	/o/	/ɔ/		⟨o⟩ /ɔ/	⟨uo⟩ /uə/	⟨o⟩ /ɔ/	⟨ue⟩ /wɛ/ > /ø/
Long O	/oː/	/o/	/o/	⟨o⟩ /o/	⟨ou⟩ /ou/	⟨o(u)⟩ /u/	⟨eu⟩ /eu/ > /ø/
Short U	/u/	/ʊ/
Long U	/uː/	/u/		⟨u⟩ /y/
AU	/aw/	/aw/		⟨o⟩ /ɔ/

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

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: /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. pēior "worse"); any consonant followed by a /j/ coming from Latin short /e/ or /i/ in hiatus (e.g. balnevm "bath", palātivm "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", veclvm < vetvlvm "old", nigrvm "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 (formerly /mɑːl(ǝ)/) "male" (Latin māscvlvm < */ˈmaslǝ/). Phonemic (although not phonetic) length disappeared by the 18th century, but the quality differences mostly remain.
• Syllables closed by /l/ followed by another consonant (although the sequence -lla- was not affected). The /l/ vocalized to /u/, 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 -nev-, -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").

Note that 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 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.

Table of modern outcomes of Vulgar Latin vowel combinations

Gallo-Romance	Context	Proto-French	Later Old French	Modern French	Example
Basic vowels
/a/	closed	/a/	/a/	/a/	partem > part /paʁ/ "part"
	closed followed by /s/		/ɑ/	/ɑ/	bassvm > bas /bɑ/
	open	/æ/	/ɛ/	/ɛ/; /e/+#	mare > mer /mɛʁ/ "sea", amātvm > /aiˈmɛθ/ > aimé /eˈme/ "loved"
	palatal + open	/iæ/	/jɛ/	/jɛ/; /je/+#	medietātem > Vulgar Latin /mejeˈtate/ > /mejˈtʲate/ > Early Old French /meiˈtiɛθ/ > Late Old French /moiˈtjɛ/ > moitié /mwaˈtje/ "half"; cārvm > Old French chier /tʃjɛr/ > cher /ʃɛʁ/ "dear"
/ɛ/	closed	/ɛ/	/ɛ/	/ɛ/	septem > sept /sɛt/ "seven"
	open	/iɛ/	/jɛ/	/jɛ/; /je/+#	heri > hier /jɛʁ/ "yesterday"; pedem > pied /pje/ "foot"
/e/	closed	/e/	/ɛ/	/ɛ/	siccvm > sec /sɛk/ "dry"
	open	/ei/	/oi/ > /wɛ/	/wa/	pēram > poire /pwaʁ/; vidēre > early Old French vedeir /vǝˈðeir/ > Old French vëoir /vǝˈoir/ > voir /vwaʁ/ "to see"
	palatal + open	/iei/	/i/	/i/	cēram > cire /siʁ/ "wax"; mercēdem > merci /mɛʁˈsi/ "mercy"
/i/	all	/i/	/i/	/i/	vītam > vie /vi/ "life"; vīllam > ville > /vil/ "town"
/ɔ/	closed	/ɔ/	/ɔ/	/ɔ/; /o/+#	portam > porte /pɔʁt/ "door"; *sottvm, *sottam > sot, sotte /so/, /sɔt/ "silly"
	closed followed by /s,z/		/o/	/o/	grossvm, grossam > gros, grosse /ɡʁo/, /ɡʁos/ "fat"
	open	/uɔ/	/wɛ/	/œ/, /ø/	novvm > neuf /nœf/ "new"; cor > *corem > cœur /kœʁ/ "heart"
/o/	closed	/o/	/u/	/u/	svbtvs > /ˈsottos/ > sous /su/ "under"; svrdvm > sourd /suʁ/ "mute"
	open	/ou/	/eu/	/œ/, /ø/	nōdvm > nœud /nø/ "knot"
/u/	all	/y/	/y/	/y/	dv̄rvm > dur /dyʁ/ "hard"; nv̄llam > nulle /nyl/ "none (fem.)"
/au/	all	/au/	/ɔ/	/ɔ/; /o/+#	avrvm > or /ɔʁ/ "gold"
	followed by /s,z/		/o/	/o/	cavsam > chose /ʃoz/ "thing"
Vowels + /n/
/an/	closed	/an/	/ã/	/ɑ̃/ [ɒ̃]	annvm > an /ɑ̃/ "year"; cantvm > chant /ʃɑ̃/ "song"
	open	/ain/	/ɛ̃n/	/ɛn/	sānam > saine /sɛn/ "healthy (fem.)"; amat > aime /ɛm/ "(he) loves"
	late closed		/ɛ̃/	/ɛ̃/ [æ̃]	sānvm > sain /sɛ̃/ "healthy (masc.)"; famem > faim /fɛ̃/ "hunger"
	palatal + late closed	/iain/ > /iɛn/	/jɛ̃/	/jɛ̃/ [jæ̃]	canem > chien /ʃjɛ̃/ "dog"
/ɛn/	closed	/en/	/ã/	/ɑ̃/ [ɒ̃]	dentem > dent /dɑ̃/ "teeth"
	open	/ien/	/jɛ̃n/	/jɛn/	tenent > tiennent /tjɛn/ "(they) hold"
	late closed		/jɛ̃/	/jɛ̃/ [jæ̃]	bene > bien /bjɛ̃/ "well"; tenet > tient /tjɛ̃/ "(he) holds"
/en/	closed	/en/			unattested?!
	open	/ein/	/ẽn/	/ɛn/	pēnam > peine /pɛn/ "sorrow, trouble"
	late closed		/ẽ/	/ɛ̃/ [æ̃]	plēnvm > plein /plɛ̃/ "full"; sinvm > sein /sɛ̃/ "breast"
	palatal + late closed	/iein/ > /in/	/ĩ/	/ɛ̃/ [æ̃]	racēmvm > raisin /rɛzɛ̃/ "grape"
/in/	closed, late closed	/in/	/ĩ/	/ɛ̃/ [æ̃]	qvīnqve > *cīnqve > cinq /sɛ̃k/ "five"; fīnvm > fin /fɛ̃/ "fine, thin (masc.)"
	open		/ĩn/	/in/	fīnam > fine /fin/ "fine, thin (fem.)"
/ɔn/	closed	/on/	/ũ/	/ɔ̃/ [õ]	pontem > pont /pɔ̃/ "bridge"
	open	/on/, /uon/	/ũn/, /wɛ̃n/	/ɔn/	bonam > bonne /bɔn/ "good (fem.)"
	late closed		/ũ/, /wɛ̃/	/ɔ̃/ [õ]	bonvm > OF buen > bon /bɔ̃/ "good (masc.)"; comes > OF cuens "count (noble rank) (nom.)"
/on/	closed, late closed	/on/	/ũ/	/ɔ̃/ [õ]	dōnvm > don /dɔ̃/ "gift"
	open		/ũn/	/ɔn/	dōnat > donne /dɔn/ "(he) gives"
/un/	closed, late closed	/yn/	/ỹ/	/œ̃/ > /ɛ̃/ [æ̃]	v̄nvm > un /œ̃/ > /ɛ̃/ "one"; perfv̄mvm > parfum /paʁˈfœ̃/ > /paʁˈfɛ̃/ "perfume"
	open		/ỹn/	/yn/	v̄nam > une /yn/ "one (fem.)"; plv̄mam > plume /plym/ "feather"
Vowels + /s/ (followed by a consonant)
/as/	closed	/ah/	/ɑː/	/ɑ/	bassvm > bas /bɑ/ "low"
/ɛs/	closed	/ɛh/	/ɛː/	/ɛ/	festam > fête /fɛt/ "feast"
/es/	closed	/eh/	/ɛː/	/ɛ/	bēstiam > bête /bɛt/ "beast"
/is/	closed	/ih/	/iː/	/i/	abȳssimvm > *abīsmvm > abîme /abim/ "chasm"
/ɔs/	closed	/ɔh/	/oː/	/o/	costam > côte /kot/ "coast"
/os/	closed	/oh/	/uː/	/u/	cōnstat > *cōstat > coûte /kut/ "(it) costs"
/us/	closed	/yh/	/yː/	/y/
Vowels + /l/ (followed by a consonant, but not /l/+/a/)
/al/	closed	/al/	/au/	/o/	falsvm > faux /fo/ "false"; palmam > paume /pom/ "palm"
/ɛl/	closed	/ɛl/	/ɛau/	/o/	bellvm > beau /bo/ (but bellam > belle /bɛl/) "beautiful"
	late closed	/jɛl/	/jɛu/	/jœ/, /jø/	melivs > /miɛʎts/ > /mjɛus/ > mieux /mjø/ "better"
/el/	closed	/el/	/ɛu/	/œ/, /ø/	capillvm > cheveu /ʃǝˈvø/ "hair"; *filtrvm > feutre /føtʁ/ "felt"
/il/	closed, late closed	/il/	/i/	/i/	gentīlem > gentil /ʒɑ̃ˈti/ "nice"
/ɔl/	closed	/ɔl/	/ou/	/u/	follem > fou (but *follam > folle /fɔl/) "crazy"; colaphvm > *colpvm > coup /ku/ "blow"
	late closed	/wɔl/	/wɛu/	/œ/, /ø/	volet > OF vueut > veut "(he) wants"
/ol/	closed	/ol/	/ou/	/u/	pvlsat > pousse /pus/ "(he) pushes"
/ul/	closed, late closed	/yl/	/y/	/y/	cv̄lvm > cul /ky/ "buttocks"
Vowels + /i/ (from a Gallo-Romance palatal element)
/ai/	all	/ai/	/ɛ/	/ɛ/	factvm > /fait/ > fait /fɛ/ "deed"; palātivm > palais /paˈlɛ/ "palace"; plāgam > plaie /plɛ/ "wound"; placet > /plaist/ > plaît /plɛ/ "(he) pleases"; paria > paire /pɛʁ/ "pair"
	palatal +	/iai/ > /i/	/i/	/i/	iacet > gît /ʒi/ "(he) lies (on the ground)"; cacat > chie /ʃi/ "(he) shits"
/ɛi/	all	/iɛi/	/i/	/i/	lectvm > /lɛit/ > lit /li/ "bed"; sex > six /sis/ "six"; pēior > pire /piʁ/ "worse"
/ei/	all	/ei/	/oi/	/wa/	tēctvm > /teit/ > toit /twa/ "roof"; rēgem > /rei/ > roi /ʁwa/ "king"; nigrvm > /neir/ > noir /nwaʁ/ "black"; fēriam > /ˈfeira/ > foire /fwaʁ/ "fair"
/ɔi/	all	/uɔi/	/yi/	/ɥi/	noctem > /nɔit/ > nuit /nɥi/ "night"; hodie > /ˈɔje/ > hui /ɥi/ "today"; coxam > /ˈkɔisǝ/ > cuisse /kɥis/ "thigh"
/oi/	all	/oi/	/oi/	/wa/	bvxitam > /ˈboista/ > boîte /bwat/ "box"; crvcem > croix /kʁwa/ "cross"
/ui/	all	/yi/	/yi/	/ɥi/	frv̄ctum > /fruit/ > fruit /fʁɥi/ "fruit"
/aui/	all	/ɔi/	/oi/	/wa/	gavdia > /ˈdʒɔiǝ/ > joie /ʒwa/ "joy"
Vowels plus /ɲ/ (from /n/ + a Gallo-Romance palatal element)
/aɲ/	closed, late closed	/aɲ/ > /ain/	/ɛ̃/	/ɛ̃/ [æ̃]	ba(l)nevm > /baɲ/ > /bain/ > bain /bɛ̃/ "bath"; sanctvm > /saɲt/ > /saint/ > saint /sɛ̃/ "holy"
	open	/aɲ/	/ãɲ/	/aɲ/	montāneam > /monˈtaɲ/ > montagne /mɔ̃ˈtaɲ/ "mountain"
/ɛɲ/	unattested?
/eɲ/	closed, late closed	/eɲ/ > /ein/	/ẽ/	/ɛ̃/ [æ̃]	pinctvm > /peɲt/ > /peint/ > peint /pɛ̃/ "painted"
	open	/eɲ/	/ẽɲ/	/ɛɲ/	insigniam > enseigne /ɑ̃ˈsɛɲ/ "sign"
/iɲ/	closed, late closed	unattested?
	open	/iɲ/	/ĩɲ/	/iɲ/	līneam > ligne /liɲ/ "line"
/ɔɲ/	closed, late closed	/oɲ/ > /oin/	/wɛ̃/	/wɛ̃/ [wæ̃]	longe > /loɲ/? > /loin/ > loin /lwɛ̃/ "far"
	open	/oɲ/	/ũɲ/	/ɔɲ/	*frogna (Gaulish) > frogne /fʁɔɲ/ "frown"
/oɲ/	closed, late closed	/oɲ/ > /oin/	/wɛ̃/	/wɛ̃/ [wæ̃]	pvnctvm > /poɲt/ > /point/ > point /pwɛ̃/ "point"; cvneum > /koɲ/ > /koin/ > coin /kwɛ̃/ "wedge"
	open	/oɲ/	/ũɲ/	/ɔɲ/	verecvndiam > vergogne /vɛʁˈɡɔɲ/ "shame"
/uɲ/	closed, late closed	/yɲ/ > /yin/	/ɥĩ/	/ɥɛ̃/ [ɥæ̃]	iv̄nivm > /dʒyɲ/ > /dʒyin/ > juin /ʒɥɛ̃/ "June"
	open	unattested?

^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/ "young" vs. jeûne /ʒøn/ [ʒøːn] "fast (abstain from food)". In general, however, only /ø/ occurs word-finally, before /z/, and usually before /t/, while /œ/ occurs elsewhere.

^3 The changes producing French moitié /mwaˈtje/ were approximately as follows:

1. medietātem (Classical 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/)

Chronological history

From Vulgar Latin through to Proto-Western-Romance

• Introduction of prosthetic short /i/ before words beginning with /s/ + consonant, becoming closed /e/ with the Romance vowel change (e.g. Spanish espina, Fr. épine "thorn, spine" < spīnam).
• Reduction of ten-vowel system of Vulgar Latin to seven vowels; diphthongs ae and oe reduced to /ɛ/ and /e/; maintenance of /au/ diphthong.
• Loss of final /-m/ (except in monosyllables, e.g. modern rien < rem).
• Loss of /h/.
• /ns/ > /s/.
• /rs/ > /ss/ in some words (e.g. dorsvm > Modern French dos), but not others (e.g. vrsvm > Modern French ours).
• Final /-er/ > /-re/, /-or/ > /-ro/ (cf. Spanish cuatro, sobre < qvattvor, svper).
• Vulgar Latin unstressed vowel loss: Loss of intertonic (i.e. unstressed and in an interior syllable) vowels between /k/, /ɡ/ and /r/, /l/.
• Reduction of /e/ and /i/ in hiatus to /j/, followed by palatalization. Palatalization of /k/ and /ɡ/ before front vowels.
  • /kj/ is apparently doubled to /kkj/ prior to palatalization.
  • /dʲ/ and /ɡʲ/ (from /dj/, /ɡj/, and /ɡ/ before a front vowel) become /j/.

To Proto-Gallo-Ibero-Romance

• /kʲ/ and /tʲ/ merge, becoming /tsʲ/ (still treated as a single sound).
• /kt/ > /jt/.
• /ks/ > /js/.
• First diphthongization (only in some dialects): diphthongization of /ɛ/, /ɔ/ to /ie/, /uo/ (later, /uo/ > /ue/) in stressed, open syllables. This also happens in closed syllables before a palatal, often later absorbed: pēior >> /ˈpejro/ > /ˈpiejro/ >> pire "worst"; noctem > /ˈnojte/ > /ˈnuojte/ >> /nujt/ nuit; but tertivm > /ˈtertsʲo/ >> tierz.
• First lenition (did not happen in a small area around the Pyrenees): chain shift involving intervocalic consonants: voiced stops and unvoiced fricatives become voiced fricatives (/ð/, /v/, /j/); unvoiced stops become voiced stops. Note: /tsʲ/ (from /k(eˌi)/, /tj/) is pronounced as a single sound and voiced to /dzʲ/, but /ttsʲ/ (from /kk(eˌi)/, /kj/) is geminate and thus not voiced. Consonants before /r/ are lenited, also, and /pl/ > /bl/. Final /t/ and /d/ when following a vowel are lenited.
• /jn/, /nj/, /jl/, /ɡl/ (from Vulgar Latin /ɡn/, /ŋɡʲ/, /ɡl/, /kl/, respectively) become /ɲ/ and /ʎ/, respectively.
• First unstressed vowel loss: Loss of intertonic (i.e. unstressed and in an interior syllable) vowels, except /a/ when pretonic. This 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 OF. However in some analyses, the standard for central French was initially for lenition to occur before this unstressed vowel apocope, and patterns where the order was reversed, resulting in voiceless consonants, were loaned from the more Frankish influened 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)

To Early Old French

In approximate order:

• Spread and dissolution of palatalization:
  • A protected /j/ (not preceded by a vowel), stemming from an initial /j/ or from a /dj/, /ɡj/, or /ɡ(eˌi)/ when preceded by a consonant, becomes /dʒ/.
  • A /j/ followed by another consonant tends to palatalize that consonant; these consonants may have been brought together by intertonic loss. (e.g., medietātem > /mejeˈtate/ > /mejˈtʲate/ > moitié. peior > /ˈpejro/ > /ˈpiejrʲe/ > pire, but impēiorāre > /empejˈrare/ > /empejˈrʲare/ > /empejˈriɛr/ > OF empoirier "to worsen")
  • Palatalized sounds lose their palatal quality and eject a /j/ into the end of the preceding syllable, when open; also into the beginning of the following syllable when it is stressed, open, and front (i.e., /a/ or /e/). Hence *cvgitāre > /kujeˈtare/ > /kujˈdare/ > /kujˈdʲare/ >> /kujˈdiɛr/ OF cuidier "to think". mansiōnātam > /mazʲoˈnada/ > /mazʲˈnada/ > /majzʲˈnjɛðə/ > OF maisniée "household".
    • /tʃ/ and /dʒ/ (including those from later sources, see below) eject a following /j/ normally, but do not eject any preceding /j/.
    • Double /ssʲ/ < /ssj/ and from various other combinations also ejects a preceding /j/.
    • Single /dz/ ejects such a /j/, but not double /tts/, evidently since it is a double sound and causes the previous syllable to close; see comment above, under lenition.
    • Actual palatal /lʲ/ and /nʲ/ (as opposed to the merely patalized varieties of the other sounds) retain their palatal nature and don't emit preceding /j/. Or rather, palatal /lʲ/ does not eject a preceding /j/ (or else, it is always absorbed, even when depalatalized); palatal /nʲ/ emits a preceding /j/ when depalatalized, even if the preceding syllable is closed (e.g., iungit > */ˈjonjet/ > /dʒoɲt/ > /dʒojnt/ joint).
    • Palatal /rʲ/ ejects a preceding /j/ as normal, but the /j/ metathesizes when a /a/ precedes, hence operārivm > /obˈrarʲo/ > /obˈrjaro/ (not */obˈrajro/) >> ouvrier "worker".
• Second diphthongization: diphthongization of /e/, /o/, /a/ to /ei/, /ou/, /ae/ in stressed, open syllables, not followed by a palatal sound (not in all Gallo-Romance). (Later on, /ei/ > /oi/, /ou/ > /eu/, /ae/ > /e/; see below.)
• Second unstressed vowel loss: Loss of all vowels in unstressed, final syllables, except /a/; addition of a final, supporting /e/ when necessary, to avoid words with impermissible final clusters.
• Second lenition: Same changes as in first lenition, applied again (not in all Gallo-Romance). Note: Losses of unstressed vowels may have blocked this change from happening.
• Palatalization of /ka/ > /tʃa/, /ɡa/ > /dʒa/.
• Further vocalic changes (part 1):
  • /ae/ > /ɛ/ (but > /jɛ/ after a palatal, and > /aj/ before nasals when not after a palatal).
  • /au/ > /ɔ/.
• Further consonant changes:
  • Geminate stops become single stops.
  • Final stops and fricatives become devoiced.
  • /dz/ > /z/, when not final.
  • A /t/ is inserted between palatal /ɲ/, /ʎ/ and following /s/ (dolēs > duels "you hurt" but colligis > */ˈkɔljes/ > cuelz, cueuz "you gather"; ivngis > */ˈjonjes/ > joinz "you join"; fīlivs > filz "son").
  • Palatal /ɲ/, /ʎ/ are depalatalized to /n/, /l/ when final or following a consonant.
    • In first-person verb forms, they may remain palatal when final due to the influence of the palatalized subjunctives.
    • /ɲ/ > /jn/ when depalatalizing, but /ʎ/ > /l/, without a yod. (*veclvm > /ˈvɛlʲo/ > /ˈviɛlʲo/ > viel "old" but cvnevm > /ˈkonʲo/ > coin. balnevm > /ˈbanjo/ > bain but montāneam > /monˈtanja/ > montagne.)
• Further vocalic changes (part 2):
  • /jej/ > /i/, /woj/ > /uj/. (placēre > /plajˈdzjejr/ > plaisir; noctem > /nuojt/ > nuit.)
  • Diphthongs are consistently rendered as falling diphthongs, i.e., the major stress is on the first element, including for /ie/, /ue/, /ui/, etc. in contrast with the normal Spanish pronunciation.

Through to Old French, c. 1100

• /f/, /p/, /k/ lost before final /s/, /t/. (dēbet > Strasbourg Oaths dift /deift/ > OF doit.)
• /ei/ > /oi/ (blocked by nasalization; see below).
• /wo/ > /we/ (blocked by nasalization; see below).
• /a/ develops allophone [ɑ] before /s/. Later, this develops into a separate phoneme; see below.
• Loss of /θ/ and /ð/. When this results in a hiatus of /a/ with a following vowel, the /a/ becomes a schwa /ə/.
• Loss of /s/ before voiced consonant (passing first through /h/), with lengthening of preceding vowel. Produces a new set of long vowel phonemes. Described more completely in the following section.
• /u/ > /y/.

To Late Old French, c. 1250–1300

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

change	condition	notes
/o/ > /u/	everywhere
/l/ > /w/	before consonants
/ue/, /eu/ > /œ/	everywhere
Rising diphthongs develop when first element of diphthong is /u/, /y/, /i/. Stress shifts to second element.	everywhere	Hence /yi/ > [yj] > [ɥi]
/oi/ > /we/.	everywhere	Later, /we/ > /ɛ/ in some words, e.g. français; note doublet François.
/ai/ > /ɛ/	everywhere	after this, ⟨ai⟩ is a common spelling of /ɛ/, regardless of origin.
/e/ > /ɛ/	In closed syllables.
Deaffrication: /ts/ > /s/ /tʃ/ > /ʃ/ /dʒ/ > /ʒ/	everywhere
Phonemization of /a/ vs. /ɑ/.	[ɑ] was initially an allophone of /a/ before /s/, /z/; that was phonemicized when /ts/ > /s/.	E.g: *[ˈtʃatsə] > /ʃas/, chasse ("he hunts"). *[ˈtʃɑsə] > /ʃɑs/, châsse ("reliquary, frame") Later losses of /s/ produced further minimal pairs.
/h/ > Ø compensatory lengthening of preceding vowel	before consonant	Around 900 /s/ > /h/ before a consonant. From borrowings into English, it appeared that this latter stage had already occurred in Old French when the following consonant is voiced but not when unvoiced. By the end of Old French a whole new set of phonemically lengthened vowels developed. Preconsonantic ⟨s⟩ was retained as a marker of vowel length until being substituted by ⟨^⟩.

To Middle French, c. 1500

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

• /au/ > /o/.
• /ei/ > /ɛ/.
• Loss of final consonants before a word beginning with a consonant. This produces a three-way pronunciation for many words (alone, followed by a vowel, followed by a consonant), which is maintained to this day in the words six "six" and dix "ten" (and until recently neuf "nine"), e.g. dix /dis/ "ten" but dix amis /diz aˈmi/ "ten friends" and dix femmes /di ˈfam/ "ten women".
• (Around this time, subject pronouns become mandatory due to loss of phonetic differences between inflections.)

(fill in further)

To Early Modern French, c. 1700

• Loss of most phonemically lengthened vowels (preserved in Belgian and Acadian French).
• Loss of final consonants in a word standing alone. This produces a two-way pronunciation for many words (in close connection with a following word that begins with a vowel vs. in all other cases), often maintained to the present day, e.g. nous voyons /nu vwaˈjɔ̃/ "we see" vs. nous avons /nuz aˈvɔ̃/ "we have". This phenomenon is known as liaison.
• oi /we/ > /wa/ (See above – Through late Old French) or /ɛ/ (e.g. étoit > était – 19th century). However, the pronunciation /we/ is preserved in some forms of Quebec French.

(fill in further)

To Modern French, c. 2000

• /r/ becomes uvular sound: trill /ʀ/ or fricative /ʁ/ (replacing the rolled r formerly often used by the clergy).
• Merger of /ʎ/, spelled as il in œuil and travail, with /j/ in the 18th century (see Mouillé)
• Loss of final /ə/. Loss of /ə/ elsewhere unless a sequence of three consonants would be produced (such constraints operate over multiword sequences of words that are syntactically connected).
• Gradual loss of liaison, unless absolutely needed, such as to distinguish quelques-uns from quelqu'un.
• In informal speech, gradual loss of the ne in negations, je n'ai pas becomes j'ai pas.
• In Metropolitan French, gradual merging of /œ̃/ and /ɛ̃/, realized as [æ̃].
• In Metropolitan French, loss of the phomene /ɑ/, merged with /a/, realized [a].

Nasalization

Progressive nasalization of vowels before /n/ or /m/ occurred over several hundred years, beginning with the low vowels, possibly as early as c. 900 AD, and finished with the high vowels, possibly as late as c. 1300. Numerous changes occurred afterwards, continuing up through the present day.

The following steps occurred during the Old French period:

• Nasalization of /a/, /e/, /o/ 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 /ɔ̃i/ occurs because /oi/ has more than one origin, e.g. coin "corner" < cvnevm. The sequences /iẽn/ or /iẽm/, and /uẽn/ or /uẽm/, also occur, but the last two occur in only one word each, 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 /ã/; but unaffected in the sequences /jẽ/ and /ẽj/ (e.g. bien, plein). The merging of /ẽ/ and /ã/ probably occurred during the 11th or early 12th century, and did not affect Old Norman or Anglo-Norman.
• Nasalization of /i/, /u/, /y/ before /n/ or /m/.

The following steps occurred during the Middle French period:

• Lowering of /ũ/ > /õ/ > /ɔ̃/. (Note that most /ũ/ come from original /õ/, as original /u/ became /y/.)
• Denasalization of vowels before /n/ or /m/ followed by a vowel or semi-vowel. (Note that 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, prove that nasalization originally operated in all environments.)
• Deletion of /n/ or /m/ after remaining nasal vowels (i.e. when not protected by a following vowel or semi-vowel). Hence dent /dɑ̃/ "tooth" < */dãt/ < OFr dent /dãnt/ < EOFr */dɛ̃nt/ < dentem.

The following steps occurred during the Modern French period:

• /ĩ/ > /ẽ/ > /ɛ̃/ > [æ̃]. This also affects diphthongs such as /ĩẽ/ > /jẽ/ > /jɛ̃/, e.g. bien /bjɛ̃/ "well" < bene; /ỹĩ/ > /ɥĩ/ > /ɥɛ̃/, e.g. juin /ʒɥɛ̃/ "June" < iv̄nivm; /õĩ/ > /wẽ/ > /wɛ̃/, e.g. coin /kwɛ̃/ "corner" < cvnevm. Note also /ãĩ/ > /ɛ̃/, e.g. pain /pɛ̃/ "bread" < pānem; /ẽĩ/ > /ɛ̃/, e.g. plein /plɛ̃/ "full (m.s.)" < plēnvm.
• /ã/ > /ɑ̃/.
• /ỹ/ > /œ̃/. In the 20th century, this sound has low functional load and has tended to merge with /ɛ̃/.

This leaves only four nasal vowels /ɛ̃/, /ɑ̃/, /ɔ̃/, and /œ̃/, and increasingly only the three /ɛ̃/, /ɑ̃/, /ɔ̃/.