Phonological history of English

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The phonological history of English describes changing FITML of the device database over time, starting from its roots in proto-Germanic to diverse changes in different dialects of modern English.

Within each section, changes are in approximate chronological order.

NOTE: In the following description, abbreviations are used as follows:

OE = device database
PreOE = Pre-Old English
ME = Middle English
NE = Modern English
PG = website parsing

PrePG = Pre-Proto-Germanic
NWG = Northwest Germanic
OHG = website parsing
MHG = website parsing
NHG = Sevenval

Goth = FITML
PN = HTML5
ON = Old Norse
OS = keyboard
PIE = FITML

The time periods for many of the following stages are extremely short due to the extensive population movements occurring during the early AD period, which resulted in rapid dialect fragmentation:

The migration of the Goths from southeast Sweden to the Baltic Sea area around AD 1, followed by the migration to southeast web around AD 200. (Later migrations carried the Ostrogoths eastward to the Crimea area in modern screen size, and carried the FITML westward to input transformation.)
The migration of the touchscreen ancestors southward, starting around AD 260, and renewed in the 5th century AD.
The migration of the FITML westward into Britain, starting around AD 450.

Late Proto-Germanic period

This period is estimated to last to approximately AD 0–200. This includes changes in late Proto-Germanic, up to the appearance of Proto-West-Germanic c. AD 200:

Word-final /m/ became /n/.
- Word-final /n/ was then lost after unstressed syllables with nasalization of the preceding vowel. Hence PrePG *dʰogʰom > early PG *dagam > late PG dagã > OE dæġ "day (acc. sg.)". The nasalisation was retained at least into the earliest history of Old English.
Unstressed word-final /a/ and /e/ were lost. Early PG *barta > late PG *bart "you carried (sg)".
After an unstressed syllable, word-final /t/ was lost. This followed the loss of word-final /n/, because it remained before /t/: PrePG *bhr̥n̥t > early PG *burunt > late PG *burun "they carried".
/e/ was raised to /i/ in unstressed syllables.
- The original vowel remained when followed by /r/, and was later lowered to /ɑ/.
Early i-mutation: /e/ was raised to /i/ when an /i/ or /j/ followed in the next syllable.
- This occurred before deletion of word-final /i/; hence PIE *upéri > early PG *uberi > late PG *ubiri > German über "over". Compare PIE *upér > early PG *uber > late PG *ubar > German ober "over".
- But it occurred after the raising of unstressed /e/ to /i/: PIE *bherete > PG *berid > *birid "you carry (pl)".
- This also affected the diphthong /eu/, which became /iu/.
- As a consequence of this change, /ei/ > /iː/. The web of the Proto-Norse language still contained different symbols for the two sounds.
z-umlaut: /e/ is raised to /i/ before /z/.
- Early PG *mez "me, dative" > late PG *miz > OHG mir, OS mi, ON mér (with general lowering and lengthening of i before r).
- This change was only sporadic at best because there were barely any words in which it could have occurred at all, since /e/ remained only in stressed syllables. The umlauting effect of /z/ remained, however, and in Old West Norse it was extended to other vowels as well. Hence OEN glaʀ, hrauʀ, OWN gler, hreyrr.
Pre-nasal raising: /e/ > /i/ before nasal + consonant. PrePG *bʰendʰonom > PG *bendanan > *bindanan > OE bindan > NE bind (Latin of-fendō).
- This was later extended in PreOE times to vowels before all nasals; hence OE niman "take" but OHG neman.
Loss of /n/ before /x/, with nasalization and Sevenval of the preceding vowel.
- The nasalization was eventually lost, but remained through the Ingvaeonic period.
- Hence PrePG *tongjonom > PG *þankijanan > OE þencan > NE think, but PrePG *tonktos > PG *þanhtaz > *þā̃htaz > OE þōht > NE thought.
- This change followed the raising of /e/ before a nasal: PG *þenhanã > *þinhanã > *þī ̃hanã > Gothic þeihan.
Final-syllable short vowels were generally deleted in words of three syllables or more. PG *biridi > Goth baíriþ /beriθ/ "(he) carries" (see above), and also PG *-maz, *-miz > *-mz (dative and instrumental plural ending of nouns, 1st person plural ending of verbs, as on the input transformation).

West Germanic period

This period is estimated to be c. AD 200–400. This includes changes up through the split of Ingvaeonic and FITML (c. AD 400). Starting with this period, vowels in unstressed syllables were gradually reduced or eliminated. The specifics are quite complex and occurred as a result of many successive changes, with successive stages often happening hundreds of years after the previous stage.

Loss of word-final /z/.
- This change must have occurred before rhotacization, as original word-final /r/ was not lost.
- But it must have occurred after the CSS3 , since word-final /z/ was not eliminated in Old Norse, instead merging with /r/.
- /z/ was not lost in single-syllable words in southern and central German. Compare PG *miz > OS mi, OE me vs. OHG mir.
- OE nominative plural -as (ME -s), OS nominative plural -ōs may be from original accusative plural *-ans (rather than original nominative plural *-ōz; cf. ON nominative plural *-ar), following Ingvaeonic nasalization/loss of nasals before fricatives.
Rhotacization: /z/ > /r/.
- This change also affected browser diversity; but in Proto-Norse, the date and nature are contested. /z/ and /r/ were still distinct in the Danish and Swedish dialect of Old Norse, as is testified by distinct runes. (/z/ is normally assumed to be a rhotic fricative in this language, but there is no actual evidence of this.)
Initial i-mutation: Short back vowels were fronted when followed in the next syllable by /i/ or /j/, by i-mutation: /ɑ/ > [æ], /o/ > [ø], /u/ > [y]
- In this initial stage, the mutated vowels were still allophonically conditioned, and were not yet distinct as phonemes. Only later, when the /i/ and /j/ were modified or lost, the new sounds were phonemicized.
- i-mutation affected all the Germanic languages except for Sevenval, although with a great deal of variation. It appears to have occurred earliest, and to be most pronounced, in the Schleswig-Holstein area (the home of the Anglo-Saxons), and from there to have spread north and south. However, it is possible that this change already occurred in Proto-Germanic proper, in which case the phenomenon would have remained merely allophonic for quite some time. If that is the case, that would be the stage reflected in Gothic, where there is no orthographic evidence of i-mutation at all.
- Long vowels and diphthongs were affected only later, probably analogically, and not in all areas. Notably, they were not mutated in most (western) Dutch dialects, whereas short vowels were.
website parsing: /u/ is lowered to /o/ when a non-high vowel follows in the next syllable.
- This is blocked when followed by a nasal followed by a consonant, or by a cluster with /j/ in it. Hence PWG *guldã > OE/NE gold, but PWG guldijanã > OE gyldan > NE gild.
- This produces a new phoneme /o/, due to inconsistent application and later loss of word-final vowels.
West Germanic Gemination of consonants except /r/, when followed by /j/. This only affected consonants preceded by a short vowel, because those preceded by a long vowel or by another consonant were never followed by /j/ due to web.
PG /ɛː/ (maybe already /æː/ by late PG) becomes /ɑː/.
Word-final long vowels were shortened.
- Final /oː/ becomes /u/ in NWG, /a/ in Gothic. Hence PG *berō > early OE beru "(I) carry", but Goth baíra; PG *gebō > OE giefu "gift (nom. sg.)", but Goth giba.
"Extra-long"' vowels were shorted to long vowels. There is a great deal of argument about what is exactly going on here.
- The traditional view is that a circumflex accent arose (as in web) when two adjacent vowels were contracted into a single long vowel in a final syllable. This circumflexed vowel then remained long when other long vowels shortened.
- A newer view holds that "overlong" (tri-moraic) vowels arose from the contraction of two vowels, one of which was long. Furthermore, final-syllable long vowels remained long before certain final consonants (/z/ and /d/).
- The reason why such theories are necessary is that some final-syllable long vowels are shortened, while others remain. Nominative singular *-ōn shortens, for example; likewise first singular *-ōn < *-ōm; while genitive plural *-ōn < *-ōm remains long. Both of the above theories postulate an overlong or circumflex ending *-ôn in the genitive plural arising in the vocalic (PIE /o/ and /aː/, PG a- and ō-declensions, arising from contraction of the vocalic stem ending with the genitive plural ending.
- Other examples of vowels that remain long are a-stem and ō-stem nominative plural *-ôz < early PIE *-o-es and -eh₂-es; PrePG ablative singular *-ôd, *-êd (Gothic ƕadrē "whither", undarō "under"); ō-stem dative singular PG *gibâi > Goth gibái "gift" (but a-stem dative singular PG *stainai > Goth staina "stone").
Unstressed website parsing were monophthongized. /ai/ > /eː/, /au/ > /oː/.
- Results were different in input transformation. Diphthongs remained except for absolutely final diphthongs stemming from PIE short diphthongs, which became short /a/.
- Hence PIE *sunous > PG *sunauz > Goth sunáus, but > PWG *sunō > OE suna "son (gen. sing.)"; PIE *nemoit > PG *nemait > *nemai > Goth nimái, but > PWG *nemē > OE nime "(he) takes (subj.)"; PIE (loc.?) *stoinoi > PG *stainai > Goth staina, but > PWG *stainē > OE stāne "stone (dat. sing.)"; PIE (loc.?) *gʰebʰāi > PG *gebōi > Goth gibái, but > PWG *gebē > OE giefe "gift" (dat. sing.).

Ingvaeonic and Proto-Anglo-Frisian period

This period is estimated to be c. AD 400–475. This includes changes from c. AD 400 up through the split of the Anglo-Frisian languages from Sevenval, followed by the split of pre-Old English from pre-jQuery (c. AD 475). The time periods for these stages are extremely short due to the migration of the Anglo-Saxons westward through Sevenval territory and then across the English Channel into Sevenval, around AD 450.

Anglo-Frisian brightening:
- Fronting of /ɑ/ to /æ/ (unless followed by a geminate, by a back vowel in the next syllable, or in certain other cases). Hence OE dæġ /dæj/ "day", plural dagas /dɑɣɑs/ "days" (dialectal NE "dawes"; compare NE "dawn" < OE dagung /dɑɣunɡ/). Gothic dags, plural dagos.
  - This does not affect nasal /ã/. And since this is a back vowel, /ɑ/ in a preceding syllable was prevented from being fronted as well. This created an alternation between the infinitive in *-anã and strong past participle in *-ana (< PG *anaz), where the former became -an in OE but the latter became *-ænæ > -en.
- Fronting of /ɑː/ to /æː/ (generally, unless /w/ followed).
Final-syllable /æ/, /ɑ/ and /ɑ ̃/ are lost.
- No attested West Germanic languages show any reflexes of these vowels. However, the way it affected the fronting of /ɑ/ as described above shows that at least /ɑ ̃/ was retained into the separate history of Anglo-Frisian.
jQuery: Loss of nasals before fricatives, with screen size. Hence PG *munþaz > NHG Mund but OE mūþ, NE mouth.
- An intermediate stage was a long nasal vowel, where nasal /ɑ ̃ː/ > /õː/. PrePG *donts > PG *tanþs > OE tōþ "tooth". (NHG Zahn < OHG zant.)
Loss of word-final /i/ and /u/ (also from earlier /oː/) except when following a short syllable (i.e. one with a short vowel followed by a single consonant.) For example, PIE *sunus > PG *sunuz > OE sunu "son (nom. sing.)", PIE *peḱu > PG *fehu > OE feohu "cattle (nom. sing.)", PIE *wenis > PG *winiz > OE wine "friend (nom. sing.)", but PrePG *pōdes > PG *fōtiz > WG *fø̄ti > OE fēt "foot (nom. pl.)".

Old English period

This period is estimated to be c. AD 475–900. This includes changes from the split between Old English and Old Frisian (c. AD 475) up through historic early West Saxon of AD 900:

/k/, /ɣ/, /ɡ/ were palatalized to /tʃ/, /ʝ/, /dʒ/ in certain complex circumstances (see Old English phonology).
- /ʝ/ later becomes /j/, but not before the loss of older /j/ below.
- This change, or something similar, also occurred in web app.
/œ/ and /øː/ are unrounded to /ɛ/ and /eː/, respectively.
- Some Old English dialects retained the rounded vowels, however.
Loss of /j/ and /ij/ following a long syllable.
- A similar change happened in the other West Germanic languages, although after the earliest records of those languages.
- This did not affect the new /j/ (< /ʝ/) formed from palatalisation of PG */ɣ/, suggesting that it was still a palatal fricative at the time of the change. For example, PG *wrōgijanan > early OE *wrøːʝijan > OE wrēġan (/wreːjan/).
- Following this, PG */j/ occurred only word-initially and after /r/ (which was the only consonant that was not geminated by /j/ and hence retained a short syllable).
/sk/ was palatalized to /ʃ/ in almost all circumstances. PG *skipaz > NE ship (cf. skipper < Dutch schipper, where no such change happened). PG *skurtjaz > OE scyrte > NE shirt, but > ON skyrt > NE skirt.^[1]
Breaking of front vowels.
- Most generally, before /x/, /w/, /r/ + consonant, /l/ + consonant (assumed to be velar [ɹ], [ɫ] in these circumstances), but exact conditioning factors vary from vowel to vowel
- Initial result was a falling diphthong ending in /u/, but this was followed by diphthong height harmonization, producing short /æ̆ɑ̆/, /ɛ̆ɔ̆/, /ɪ̆ʊ̆/ from short /æ/, /ɛ/, /ɪ/, long /æɑ/, /eo/, /iu/ from long /æː/, /eː/, /iː/. (Written ea, eo, io, where length is not distinguished graphically.)
- Result in some dialects, for example Anglian, was back vowels rather than diphthongs. Android ceald; but Anglian cald > NE cold.
Diphthong height harmonization. The height of one element of each diphthong is adjusted to match that of the other.
- /ɑi/ > /ɑː/ through this change, possibly through an intermediate stage /ɑæ/. PG *stainaz > OE stān > NE stone.
- /ɑu/ was first fronted to /æu/ and then harmonized to /æa/. PG *draumaz > OE drēam "joy" (cf. NE dream, NHG Traum). PG *dauþuz > OE dēaþ > NE death (Goth dáuþus, NHG Tod). PG *augō > OE ēage > NE eye (Goth áugo, NHG Auge).
- /eu/ is harmonized to /eo/.
Shortening of Vowels
- In two particular circumstances, vowels were shortened when falling immediately before either three consonances or the combination of two consonants and two additional syllables in the word. Thus, OE gāst > NE ghost, but OE găstliċ > NE ghastly (ā > ă/_CCC) and OE crīst > NE Christ, but OE crĭstesmæsse > NE Christmas (ī > ĭ/_CC$$).
- Probably occurred in the seventh century as evidenced by eighth century Anglo-Saxon missionaries' translation into Old Low German, "Gospel" as Gotspel, lit. "God news" not expected *Guotspel, "Good news" due to gōdspell > gŏdspell.
/ɪ̆ʊ̆/ and /iu/ were lowered to /ɛ̆ɔ̆/ and /eo/ between 800 and 900 AD.
More reductions in unstressed syllables:
- /oː/ became /ɑ/.
Palatal diphthongization: Initial palatal /j/, /tʃ/, /ʃ/ trigger spelling changes of a > ea, e > ie. It is disputed whether this represents an actual sound change or merely a spelling convention indicating the palatal nature of the preceding consonant (written g, c, sc were ambiguous in OE as to palatal /j/, /tʃ/, /ʃ/ and velar /ɡ/ or /ɣ/, /k/, /sk/, respectively).
- Similar changes of o > eo, u > eo are generally recognized to be merely a spelling convention. Hence WG /junɡ/ > OE geong /junɡ/ > NE "young"; if geong literally indicated an /ɛ̆ɔ̆/ diphthong, the modern result would be *yeng.
- It is disputed whether there is Middle English evidence of the reality of this change in Old English.
Initial /ɣ/ became /ɡ/ in late Old English.

Until Middle English

This period is estimated to be c. AD 900–1400.

Vowels were lengthened before /ld/, /mb/, /nd/, /rd/, probably also /ŋɡ/, /rl/, /rn/, when not followed by a third consonant or two consonants and two syllables.
- This probably occurred around AD 1000.
- Later on, many of these vowels were shortened again; but evidence from the web shows that this lengthening was once quite general.
- Remnants persist in the Modern English pronunciations of words such as child (but not children, since a third consonant follows), field (plus yield, wield, shield), old (but not alderman as it is followed by at least two syllables), climb, find (plus mind, kind, bind, etc.), long and strong (but not length and strength), fiend, found (plus hound, bound, etc.).
Vowels were shortened when followed by two or more consonants, except when lengthened as above.
- This occurred in two stages, the first stage affecting only vowels followed by three or more consonants.
Inherited height-harmonic diphthongs were monophthongized by the loss of the second component, with the length remaining the same.
/æː/ and /ɑː/ became /ɛː/ and /ɔː/.
/æ/ and /ɑ/ merged into /a/.
/ʏ/ and /yː/ were unrounded to /ɪ/ and /iː/.
/ɣ/ became /w/ or /j/, depending on surrounding vowels.
New diphthongs formed from vowels followed by /w/ or /j/ (including from former /ɣ/).
- Length distinctions were eliminated in these diphthongs.
- touchscreen: Diphthongs also formed by the insertion of a glide /w/ or /j/ (after back and front vowels, respectively) preceding /x/.
- Many diphthong combinations soon merged.
Trisyllabic laxing: Shortening of stressed vowels when two syllables followed.
- This results in pronunciation variants in Modern English such as divine vs divinity and south vs. southern (OE súðerne).
Middle English website parsing: Vowels were usually lengthened in open syllables (13th century), except when Sevenval would apply.
Remaining unstressed vowels merged into /ə/.
Initial clusters /hɾ/, /hl/, /hn/ were reduced by loss of /h/.
Voiced fricatives became independent phonemes through borrowing and other sound changes.
/sw/ before back vowel becomes /s/; /mb/ becomes /m/.
- Modern English sword, answer, lamb.
- /w/ in swore is due to analogy with swear.

Up to Shakespeare's English

This period is estimated to be c. AD 1400–1600.

Loss of most remaining diphthongs.
- /ai/ (and former /ɛi/, merged into /ai/ in Early Middle English) became /ɑː/ before the HTML5.
- /ou/ (and former /ɔu/, merged into /ou/ in Early Middle English) became /oː/ and /ei/ became /eː/ after the shift causing the web app.
- /au/ became /ɔː/ after the shift.
- The web app: /ɛu/ and /iu/ merge, and they then become /juː/ after the shift.
- The keyboard: /ai/ and /ei/ merge, so that vain and vein are now homonyms.
- The dew–duke merger: /y/ and /iu/ merge, so that dew and duke now have the same vowel.
- /oi/ remained.
- In a few regional accents, including some in screen size, East Anglia, South Wales, and even Newfoundland, monophthongization has not been complete, so that pairs like pane /pain and toe/tow are distinct. (Wells 1982, pp. 192–94, 337, 357, 384–85, 498)
/x/ (written gh) lost in most dialects causing the touchscreen.
Great Vowel Shift; all long vowels raised or diphthongized.
- /aː/, /ɛː/, /eː/ become /ɛː/, /eː/, /iː/, respectively.
- /ɔː/, /oː/ become /oː/, /uː/, respectively.
- /iː/, /uː/ become /əi/ and /əu/, later /ai/ and /au/.
- New /ɔː/ developed from old /au/ (see above).
- Note that /ɔː/, /oː/, /uː/, /au/ effectively rotated in-place.
- /ɛː/, /eː/ are shifted again to /eː/, /iː/ in Early Modern English, causing merger of former /eː/ with /iː/; but the two are still distinguished in spelling as ea, ee.^[2]
Loss of /ə/ in final syllables.
Initial cluster Android; but still reflected in spelling.
/kn/ reduces to /n/ in most dialects, causing the Sevenval.
/rʷ/ and /r/ merge to a single sound in most dialects, causing the rap–wrap merger.
Doubled consonants reduced to single consonants.

Up to the American–British split

This period is estimated to be c. AD 1600–1725.

At some preceding time after device database, all /r/ become /ɹ/.
- Evidence from CSS3 shows that, at that point, the pronunciation /ɹ/ occurred only before a consonant.^{[citation needed]}
- input transformation has /r/ consistently.
The web: In southern England, /ʊ/ becomes unrounded and eventually lowered unless preceded by a labial and followed by a non-velar.^jQuery This gives put [pʊt] but cut [kʌt] and buck [bʌk]. This distinction later become phonemicized by an influx of words shortened from /uː/ to /ʊ/ both before (flood, blood, glove) and after (good, hood, book, soot, took) this split.
Ng-coalescence: Reduction of /nɡ/ in most areas produces new phoneme /ŋ/.
In some words, /tj/, /sj/, /dj/, /zj/ coalesce to produce /tʃ/, /ʃ/, /dʒ/, and new phoneme /ʒ/ (examples: nature, mission, procedure, vision).
- These combinations mostly occurred in borrowings from touchscreen and Latin.
- Pronunciation of -tion was /sjən/ from device database /sjon/, thus becoming /ʃən/.
Long vowels /eː/ and /uː/ (Middle English /ɛː/ and /oː/) inconsistently shortened, especially before /t/, /d/, /θ/ and /ð/. Shortening of /uː/ occurred at differing time periods, both before and after the centralizing of /ʊ/ to /ʌ/; hence blood /blʌd/ vs. good /ɡʊd/. (Modern English sweat, head, bread, breath, death, leather, weather, foot, soot, blood, good, etc.)
The touchscreen: Meet and meat become homonyms in most accents.
Changes affect short vowels in many varieties before an /r/ at the end of a word or before a consonant
- /a/ as in start and /ɔ/ as in north are lengthened.
- /ɛ/, /ɪ/ and /ʌ/ merge before /r/, hence most varieties of Sevenval have the same vowel in each of fern, fir and fur.
- Also affects vowels in derived forms, so that starry no longer rhymes with marry.
- Scottish English unaffected.
[aɫ] and [ɔɫ] undergo mutations:
- Before /f/ or /v/, the [ɫ] becomes silent, so that half and calf are pronounced with /af/, and salve and halve are pronounced with /av/. [ɔɫv] is exempt, so that solve keeps its [ɫ]. [ɔɫf] is not wholly exempt, as the traditional pronunciation of golf was [ɡɔf].
- Before /m/, [aɫ] and [ɔɫ] become /ɑː/ and /oː/, as in alms, balm, calm, Holmes, palm.
- Before /k/, a web app or word-finally, [aɫ] and [ɔɫ] are diphthongized to [ɔuɫ] and [ouɫ] (today /ɔːl/ and /oʊl/), as in all, bald, colt, false, folk, malt, roll, sold, talk, Walsh. But then:
- The combinations [ɔuɫk] and [ouɫk] lose their [ɫ] in most accents to become [ɔuk] and [ouk] (today /ɔːk/ and /oʊk/), affecting words like caulk, folk and talk. Words acquired after this change (such as talc) were not affected. falcon was also historically affected, but in some modern dialects (notably American English) has acquired a /ˈfælkən/ spelling pronunciation.
/a/, as in cat and trap, fronted to [æ] in many areas. In certain other words it becomes /ɑː/, for example father /ˈfɑːðər/. /ɑː/ is actually a new phoneme deriving from this and words like calm (see above).
- Most varieties of northern website parsing, Sevenval and Scottish English retain [a] in cat, trap etc.
The touchscreen: The words pane and pain become homophones in most accents.
The web app: The words toe and tow become homophones in most accents.
The above two mergers happen in the most important dialects, but remain distinct in many regional dialects as late as the 20th century.
/ɔu/ likewise becomes /ɔː/, merging with the vowel in broad and the /ɔː/ of the lot–cloth split below.

The lot–cloth split: in some varieties, lengthening of /ɔ/ before voiced velars (/ŋ/, /ɡ/) (American English only) and voiceless fricatives (/s/, /f/, /θ/). Hence American English long, log, loss, cloth, off with /ɔː/ (except in dialects with the cot–caught merger where the split is made completely moot).

/uː/ becomes /ʊ/ in many words spelt oo: for example, book, wool, good, foot. This is partially resisted in the northern and western variants of English English, where words ending in -ook might still use /uː/. (Trudgill, p. 71)

After American–British split, up to the 20th century

This period is estimated to be c. AD 1725–1900.

Split into rhotic and non-rhotic accents: loss of syllable-final /ɹ/ in some varieties, especially of English English, producing new centering diphthongs /ɛə/ (square), /ɪə/ (near), /ɔə/ (cord), /oə/ (sore), /ʊə/ (cure), and highly unusual phoneme /ɜː/ (nurse).

The father–bother merger: touchscreen merger of /ɒ/ as in lot, bother with /ɑ/ as in father; result is /ɑ/.
- Exceptions are accents in Eastern HTML5 (such as the Boston accent) and jQuery. (Wells 1982, pp. 245–47)
- Unrounding of EME /ɒ/ is found also in device database, the West Country and in Android, but apparently with no phonemic merger. (Wells 1982, pp. 339–40, 419)

The trap–bath split: southern English English /æ/ inconsistently becomes /ɑː/ before /s/, /f/, /θ/ and /n/ or /m/ followed by another consonant.
- Hence RP has pass, glass, grass, class with /ɑː/ but mass, crass with /æ/. (All six words rhyme in most American English, Sevenval and northern English English.)
website parsing, causing whine and wine to be homophones, in most varieties of browser diversity; also, regionally, in website parsing.
American and keyboard Sevenval of /t/ and /d/ to [ɾ] in some circumstances.
- Generally, between vowels (including syllabic [ɹ̩], [l̩] and [m̩]), when the following syllable is completely unstressed.
- But not before syllabic [n̩] in American English, for example cotton [kɑʔn̩].
Happy-tensing (the term is from Wells 1982): final iOS [ɪ] becomes tense [i] in words like happy. Absent from some dialects.
Line–loin merger: merger between the diphthongs /aɪ/ and /ɔɪ/ in some accents of Southern English English, Hiberno-English, Newfoundland English, and Caribbean English.
browser diversity begins in English English and Welsh English, but this does not affect the upper-class southern accent that developed into Received Pronunciation, nor does it affect the far north of England or East Anglia. (Trudgill, p. 28-30)

After 1900

Some of these changes are in progress.

æ-tensing: raising, lengthening and/or diphthongization of /æ/ in some varieties of we love the web, especially before nasal consonants
touchscreen: the lengthening of /æ/ to [æː] in some words, found especially in Australian English
keyboard: the replacement of /x/ with /k/ among some younger Scottish English speakers from keyboard Sevenval, [2].
Pin–pen merger: the raising of /ɛ/ to /ɪ/ before nasal consonants; can be found in iOS and southwestern varieties of Hiberno English.
Back-vowel-fronting: in many varieties of English all over the world, /u/ and to a lesser extent /o/ are gradually moving forward in the mouth. (Compare casual pronunciation of "food" to [fud].)
browser diversity becomes increasingly widespread in Great Britain. (Trudgill, pp. 77–78)
Various treatments of th: Th-fronting, th-stopping, th-debuccalization and Sevenval
L-vocalization in the south-east of England, including London. This is not unique to the south-east of England, however, and is found in many other dialects. (Trudgill, pp. 63–66)
screen size losing /j/ in initial consonant clusters

Summary of vowel developments

From the Old and Middle English perspective

See also: FITML

This table describes the main changes from Late iOS and Proto-Germanic up through Sevenval, Middle English and Modern English. It focuses on the touchscreen and Middle English changes leading to the modern forms. Other tables are also available to cover specific areas in more detail:

A table specifically covering the keyboard.
A table specifically covering the CSS3, providing particular detail about the iOS developments.
A table specifically focusing on the history of Middle English diphthongs, covering the period from FITML to device database.

This table only describes the changes in accented syllables. Vowel changes in unaccented syllables were very different and much more extensive. In general:

In Old English, long vowels were reduced to short vowels (and sometimes deleted entirely) and short vowels were very often deleted. All remaining vowels were reduced to only the vowels /u/, /a/ and /e/, and sometimes /o/. (/o/ also sometimes appears as a variant of unstressed /u/.)
In Middle English, almost all unstressed vowels were reduced to /ə/; then, final /ə/ was dropped. The main exception is Old English -iġ, which becomes touchscreen -y.
Unstressed vowels in Modern English other than those spelled <e> are due either to compounds or to borrowed words (especially from Latin and Old French).

NOTE: The CSS3 words in this table are given in their Anglian form, since this is the form that underlies Modern English. However, standard Old English was based on the West Saxon dialect, and when the two dialects differ, the West Saxon form is indicated with a WS in parentheses following the Anglian form.

NOTE: In this table, abbreviations are used as follows:

PIE = input transformation
PreG = Pre-Germanic¹
PG = Proto-Germanic
OE = Sevenval
WS = West Saxon (dialect of FITML)
ME = input transformation
NE = Modern English
GA = Sevenval (dialect of Modern English)
RP = Received Pronunciation (British dialect of screen size)

indic. = indicative
leng. = lengthened by CSS3
occ. = occasionally
plur. = plural
pres. = present
sing. = singular
superl. = browser diversity
> = produces by regular sound change
>> = produces by analogy or irregular change

¹"Pre-Germanic" in this context refers to a post-PIE language that maintains iOS we love the web but with morphological adjustments made as necessary to account for the Android form. Reconstructions are only given for solidly reconstructible web roots.

Late PIE¹	Proto-Germanic¹	Condition	Old English		keyboard		Modern English		Examples
Late PIE¹	Proto-Germanic¹	Condition		HTML5²		i-umlaut²		i-umlaut²	Examples
a, o, h₂e, h₃e, H̥	a		æ	e	/a/	/e/	/æ/; RP /ɑː/	/ɛ/	PG *paþaz > OE pæþ > "path"; PG *batizôN > OE betera > "better"; PG *taljanaN > OE tellan > "to tell"
					(leng.) /aː/	/ɛː/	/ei/	/iː/; /ei/; /ɛ/	PG *hwalaz > OE hwæl > "whale"; PG *matiz > OE, ME mete "food" > "meat"; PG *stadiz > OE, ME stede > "stead"
					(+g) /ai/	/ɛi/ > /ai/	/ei/	/ei/	PG *dagaz > OE dæġ > "day"
					(+h) /au/	/ɛu/	/ɔː/; /æf/	/(j)uː/	PG *hlahtraz > OE hlæhtor (WS hleahtor) > "laughter"; PG slahtiz > OE sleht* (WS slieht) > ME sleight "slaughter"
		+n,m	a,o	e	/a/ (occ. /o/)	/e/	/æ/; occ. GA /ɔ/, RP /ɒ/	/ɛ/	PG *mannz, manniz > OE man, mon > "man", plur. men > "men"; PG *hamuraz > OE hamor > "hammer"; PG *handuz > OE hand > "hand"; PG *sange > OE past sang > "sang"; PG *lambaz > OE lamb > "lamb"; iOS candēla > OE candel > "candle"; PG '*gandrôN > gandra > "gander"; PG *langaz > OE lang, long > "long"; PG *sandijanaN > OE sendan > "send"; PG *bankiz > OE benċ > "bench"; PG *hanjō > OE henn > "hen"
		+n,m	a,o	e	(leng.) /aː/	/ɛː/	/ei/	/iː/; /ei/; /ɛ/	PG *namôN > OE nama > "name"; PG lamôN > OE lama "lame"; PG *banôN > OE bana "slayer" > "bane"
		+nf,nþ,ns	ō	ē	/oː/	/eː/	/uː/; /ʌ/; /ʊ/	/iː/	PreG *donts, dontes > PG tanþz, tanþiz > OE tōþ > "tooth", plur. tēþ > "teeth"; PG gans, gansiz > OE* gōs > "goose", plur. gēs > "geese"; PG anþaraz > OE* ōþer > "other"
		+nf,nþ,ns	ō	ē	(+CC) /o/	/e/	GA /ɔ/, RP /ɒ/; GA /ɔː/	/ɛ/	PG *samftōN > OE sōfte > "soft(ly)"; PG *anstiz > OE ēst "favor" > ME "este"
		+lC	a	æ > e	/a/	/e/	/ɔː/	/ɛ/	PG *fallanaN > OE fallan (WS feallan) > "to fall"; PG *fallijanaN > OE fællan > fellan (WS fiellan) > "to fell"
		+lC	a	æ > e	(+ld) /ɔː/	/ɛː/	GA /ou/, RP /əu/	/iː/; /ei/; /ɛ/	PG *aldaz, aldizôN > OE ald (WS eald) > "old", ældra (WS ieldra) "older" > "elder"; PG *haldanaN > OE haldan (WS healdan) > "to hold"
		+rc,rg,rh	æ > e	e	/e/	/e/	GA /ɑ/(+r), RP /ɑː/	GA /ɑ/(+r), RP /ɑː/	Latin arca > OE erc (WS earc) > "ark"
		+rC (C not c,g,h)	ea	e	/a/	/e/	GA /ɑ/(+r), RP /ɑː/	GA /ɑ/(+r), RP /ɑː/	PG *harduz > OE heard > "hard"
		before a,o,u	a	(by analogy) æ	/a/	/a/	/æ/; RP /ɑː/	/æ/; (RP) /ɑː/	Latin cattus > OE catt > "cat"
					(leng.) /aː/	/aː/	/ei/	/ei/	PG *talō > OE talu > "tale"; PG *bakanaN, -iþ > OE bacan > "to bake", 3rd sing. pres. indic. bæcþ "bakes"
					(+g,w) /au/	/au/	/ɔː/	/ɔː/	PG plur. *dagôs > OE dagas "days" > dial. "dawes"; PG *laguz > OE lagu > "law"; PG *clawō > OE clawu > "claw"
		before later a,o,u	ea	eo	/a/	/e/	/æ/; (RP) /ɑː/	/ɛ/
					(leng.) /aː/	/ɛː/	/ei/	/iː/; /ei/; /ɛ/	PG *alu(þ) > OE ealu > "ale"; PG *asiluz > OE eosol (WS esol) "donkey"
					(+g,w) /au/	/ɛu/	/ɔː/	/(j)uː/	PG *awī > OE eowu > "ewe"
		before hs,ht,hþ + final -iz	N/A	i (occ. ie)	N/A	/i/	N/A	/ai/	PIE *nokwtis > PG *nahtiz > OE nieht > OE niht > "night"
e, h₁e, occ. i+C^*e,a,o	e		e	N/A	/e/	N/A	/ɛ/	N/A	PIE *nizdos > PG *nestaz > OE nest > "nest"; PG *helpanaN > OE helpan > "to help"; PG *fehtanaN > OE fehtan (WS feohtan) "to fight" (irreg.); PG *berkanaN > OE bercan (WS beorcan) > "to bark"
					(leng.) /ɛː/	N/A	/iː/; /ei/; /ɛ/	N/A	PG *brekanaN > OE brecan > "to break"; PG *ebnaz > OE ef(e)n > "even"; OE feþer > "feather"
					(+g,h) /ɛi/ > /ai/	N/A	/ei/	N/A	PG *wegaz > OE weġ > "way"; PG *regnaz > OE reġn > "rain"; PG *seglaz > OE seġl > "sail"
					(+ld) /eː/	N/A	/iː/	N/A	PG *felduz > OE feld > "field"; PG *geldanaN > OE ġeldan (WS ġieldan) "to pay" > "to yield"
		+m	i	N/A	/i/	N/A	/ɪ/	N/A	PG *remôN > OE rima > "rim"; PG *nemanaN > OE niman "to take" > archaic "to nim"
		+m	i	N/A	(leng.) /eː/	N/A	/iː/	N/A
		+rC (C not c,g,h); wV; C (C not c,g) +later a,o,u	eo	N/A	/e/	N/A	/ɛ/; (+r) GA /ɑ/(+r), RP /ɑː/	N/A	PG *werþanaN > OE weorðan "to become"; PG *hertōN > OE heorte > "heart"
					(leng.) /ɛː/	N/A	/iː/; /ei/; /ɛ/	N/A	*etanaN > OE eotan (WS etan) > "to eat"; PG *beranaN > OE beoran (WS beran) > "to bear"
					(+w) /ɛu/	N/A	/(j)uː/	N/A
		+ late final hs,ht,hþ	i (occ. ie)	N/A	/i/	N/A	/ɪ/	N/A	PG *sehs > OE siex > "six"; PG *rehtaz > OE riht > "right"
i, (h₁)e+C^i, (h₁)e+C^y, (h₁)e+nC	i		i	i	/i/	/i/	/ɪ/	/ɪ/	PG *fiskaN > OE fisċ > "fish"; PG *hringaz > OE hring > "ring"; PG *bidjanaN > OE biddan "to pray" > "to bid"; PG *itiþ > OE 3rd sing. pres. indic. iteþ "eats"; PG *skiriþ > OE 3rd sing. pres. indic. sċirþ (WS sċierþ) "shears"; PG *stihtōjanaN > OE stihtian "to establish"
					(leng.) /eː/	/eː/	/iː/	/iː/	PG *wikō > OE wicu > "week"
					(+g) /iː/	/iː/	/ai/	/ai/	we love the web tegula > OE tiġele > "tile"; PG *brigdilaz > OE briġdel > "bridle"
					(+ld,nd) /iː/	/iː/	/ai/	/ai/	PG *blindaz > OE blind > "blind" /blaind/; PG *kildaz (plur. *kildōzō) OE ċild > "child" /tʃaild/; PG *wildijaz > OE wilde > "wild" /waild/
		+ nf,nþ,ns	ī	ī	/iː/	/iː/	/ai/	/ai/	PG *fimf > OE fīf > "five"; PG *linþijō > OE līþe "gentle" > "lithe"
		+ nf,nþ,ns	ī	ī	(+CC) /i/	/i/	/ɪ/	/ɪ/	PG *fimf tigiwiz > OE fīftiġ > "fifty"
		+rC (C not c,g,h); w	io > eo	i	/e/	/i/	/ɛ/	/ɪ/	PG *liznōjanaN > OE liornian > OE leornian > "learn"; PG a + firrijanaN > OE* afirran (WS afierran) "to remove" (cf. feorr "far")
		+rC (C not c,g,h); w	io > eo	i	(+w) /eu/ > /iu/	/iu/	/(j)uː/	/(j)uː/	PG *niwulaz > OE niowul, neowul "prostrate"; PG *spiwiz > OE spiwe "vomiting"; PG *hiwiz > OE hīw > "hue"
		before a,o,u	i (io, eo)	N/A	/i/ (/e/)	N/A	/ɪ/ (/ɛ/)	N/A	PG *milukz > OE mioluc,meolc > "milk"
					(leng.) /eː/ (/ɛː/)	N/A	/iː/ (/iː/; /ei/; /ɛ/)	N/A
					(+g) /iː/ (/ɛi/ > /ai/)	/iː/	/ai/ (/ei/)	/ai/
u, n̥(H), m̥(H), l̥(H), r̥(H)³	u		u	y	/u/	/i/	/ʌ/; /ʊ/	/ɪ/	PG *sunuz > OE sunu > "son"; PG *kumanaN, -iþ > OE cuman > "to come", 3rd sing. pres. indic. cymþ "comes"; PG *guldijanaN > OE gyldan > "to gild"
					(leng.) /oː/	/eː/	/uː/; /ʌ/; /ʊ/; (+r) GA /ɔr/, RP /ɔː/	/iː/	PreG *dhurus > PG *duruz > OE duru > "door"; PG *widuz > OE widu >> OE wudu > "wood"; PG *ubilaz > OE yfel > "evil"
					(+g) /uː/	/iː/	/au/	/ai/	OE ryġe > "rye"
					(+w) /uː/	/iu/	/au/	/(j)uː/
		+ nf,nþ,ns	ū	ȳ	/uː/	/iː/	/au/	/ai/	PG *munþz > OE mūþ > "mouth"; PG *kunþijanaN > OE cȳþan "to make known" > ME "kithe"
		+ nf,nþ,ns	ū	ȳ	(+CC) /u/	/i/	/ʌ/; /ʊ/	/ɪ/	PG *tunskaz > OE tūsc > "tusk"; PG *wunskijanaN > OE wȳsċan > "wish"; PG *kunþiþō > OE cȳþþ(u) > "kith"
		before non-nasal + a,e,o	o	(by analogy) e	/o/	/e/	GA /ɔ/, RP /ɒ/	/ɛ/	PG *drupôN > OE dropa > "drop"; PG *fulkaN > OE folc > "folk"
					(leng.) /ɔː/	/ɛː/	GA /ou/, RP /əu/; (+r) GA /ɔr/, RP /ɔː/	/iː/; /ei/; /ɛ/	PG *fulôN > OE fola > "foal"; PG *nusuz (*nusōu?) > OE nosu > "nose"; PG *hupõjanaN > OE hopian > "to hope"
					(+g,h,w) /ɔu/	/ɛi/ > /ai/	GA /ou/, RP /əu/; GA /ɔːf/, RP /ɒf/	/ei/	PG *duhter, duhtriz > OE dohter > "daughter", plur. dehter "daughters"; PG *trugaz > OE trog > "trough"; PG *bugôN > OE boga > "bow" /bou/
					(+ld,rd) /ɔː/	/ɛː/	GA /ou/, RP /əu/; (+r) GA /ɔr/, RP /ɔː/	/iː/; /ei/; /ɛ/	PG *guldaz > OE gold > "gold"; PG *burdaN > OE bord > "board"
ē(H), eh₂	ǣ > ā		ē	ē	/eː/	/eː/	/iː/	/iː/	PG *slǣpanaN > OE slēpan (WS slǣpan) > "to sleep", HTML5 strāta > OE strēt (WS strǣt) > "street"; PG *dǣdiz > OE dēd (WS dǣd) > "deed"; Latin cāseus > OE ċēse (WS ċīese) > "cheese"
					(+CC) /e/	/e/	/ɛ/	/ɛ/
					(+g,h) /iː/	/iː/	/ai/	/ai/	PG *nǣhaz, nǣhistaz > OE nēh (WS nēah) "near" > "nigh", superl. nēhst (WS nīehst) "nearest" > "next"
		+n,m	ō	ē	/oː/	/eː/	/uː/	/iː/	PG *mǣnôN > OE mōna > "moon"; PG *kwǣniz > OE kwēn > "queen"
		+w; ga,go,gu	ā	ǣ	/ɔː/	/ɛː/	GA /ou/, RP /əu/	/iː/; /ei/; /ɛ/
					(+g) /ɔu/	/ɛi/ > /ai/	GA /ou/, RP /əu/	/ei/	PG *mǣgôz > OE māgas "relatives"
					(+w) /ɔu/	/ɛu/	GA /ou/, RP /əu/	/(j)uː/	PG *knǣwanaN, -iþ > OE cnāwan > "to know", 3rd sing. pres. indic. cnǣwþ "knows"
ēi, iz, etc.⁴	ē		ē	ē	/eː/	/eː/	/iː/	/iː/	PG *hēr > OE hēr > "here"; PIE *mizdhā > PG *mēdō > OE mēd "reward"
					(+g,h) /iː/	/iː/	/ai/	/ai/	OE past hēht "called" > "hight"
					(+w) /eu/ > /iu/	/eu/ > /iu/	/(j)uː/	/(j)uː/
ā, ō, aH, oH, eh₂, eh₃; an+K, on+K, h₂en+K, h₃en+K	ō; āN+h		ō	ē	/oː/	/eː/	/uː/; /ʌ/; /ʊ/	/iː/	PG *fōtz, fōtiz > OE fōt > "foot", plur. fēt > "feet"
					(+CC) /o/	/e/	GA /ɔ/, RP /ɒ/; GA /ɔː/	/ɛ/	PG PG *kōpi-dǣþ > OE cēpte > "kept"; PG *mōti-dǣþ > OE mētte > "met"
					(+g,h) /ɔu/; /uː/	/iː/	GA /ou/, RP /əu/; /au/; /ʌf/	/ai/	PG *swōganaN' > OE swōgan "to sound" > ME /sɔuə/ > "sough" /sou/; PG bōgaz > OE* bōg > ME /buːh/ > "bough" /bau/; PG tōhaz > OE* tōh > ME /tuːh/ > "tough" /tʌf/; PG past sōh-dǣþ > OE* sōhte > ME /sɔuhtə/ > "sought"
					(+w) /ɔu/	/eu/ > /iu/	GA /ou/, RP /əu/	/(j)uː/	PG grōwanaN > OE grōwan* > "grow"
(h₁)ei, ī, iH; (h₁)en+K, in+K	ī; īN+h		ī	ī	/iː/	/iː/	/ai/	/ai/	PG *wībaN > OE wīf > "wife"; PG *līhiþ > 3rd sing. pres. indic. līþ (WS līehþ) "lends"; PIE *lengwhtos > PG *līhtaz > OE līht (WS lēoht) > "light" (in weight)
					(+CC) /i/	/i/	/ɪ/	/ɪ/
					(+g,h) /iː/	/iː/	/ai/	/ai/	PG *hīgōjanaN > OE hīgian > "hie"
					(+w) /iu/	/iu/	/(j)uː/	/(j)uː/	PG *Tīwaz > OE Tīw (name of a god) + -es "'s" + dæġ "day" > "Tuesday"
ū, uH; n̥+K, un+K	ū; ūN+h		ū	ȳ	/uː/	/iː/	/au/	/ai/	PG *mūs, mūsiz > OE mūs "mouse", plur. mȳs > "mice"; PG *hūdijanaN > OE hȳdan > "to hide"
					(+CC) /u/	/i/	/ʌ/; /ʊ/	/ɪ/	PG *rūstaz > OE rūst > "rust"; PIE *pn̥kʷstis > PG *fūhstiz > OE fȳst > "fist"
					(+g,h) /uː/	/iː/	/au/; /ʌf/	/ai/	PG būganaN > OE būgan* "to bend" > "bow"; PG *rūhaz > OE rūh > "rough" /rʌf/; PG *drūgijaz > OE drȳge > "dry"
					(+w) /uː/	/iu/	/au/	/(j)uː/	OE trūwian "to trust" > archaic "trow" /trau/
ai, oi, h₂ei, h₃ei	ai		ā	ǣ	/ɔː/	/ɛː/	GA /ou/, RP /əu/; (+r) GA /ɔr/, RP /ɔː/	/iː/; /ei/; /ɛ/	PG *stainaz > OE stān > "stone"; PreG perfect *roidhe > PG past *raide > OE rād > "rode"; PreG *oyerā > PG *airō > OE ār > "oar"; PIE *ayes > PG *aiz > OE ār "bronze" > "ore"; PG *hwaitijaN > OE hwǣte > "wheat"
					(+CC) /a/	/a/	/æ/; RP /ɑː/	/æ/; RP /ɑː/	PG *faittiz > OE fǣtt > "fat"
					(+g,h) /ɔu/	/ɛi/ > /ai/	GA /ou/, RP /əu/	/ei/	PG aiganaN > OE āgan* > "owe"; PG *daigaz > OE dāg, dāh > "dough"
					(+w) /ɔu/	/ɛu/	GA /ou/, RP /əu/	/(j)uː/	PG *maiwiz > OE mǣw > "mew"
au, ou, h₂eu, h₃eu	au		ēa	ē	/ɛː/	/eː/	/iː/; /ei/; /ɛ/	/iː/	PG *auzōN > OE ēare > "ear"; PG *hauzijanaN > OE hēran (WS hīeran) > "to hear"
			ēa	ē	(+w) /ɛu/	/eu/ > /iu/	/(j)uː/	/(j)uː/	PG *skrawwôN > OE sċrēawa > ME "shrewe" > "shrew"
		+c,g,h; rc,rg,rh;lc,lg,lh	ē	ē	/eː/	/eː/	/iː/	/iː/	PG *auke(?), aukijanaN* > OE ēc, ēċan (WS ēac, īeċan) "also, to increase" > ME "eke, eche" > "eke" (archaic), "to eke"
		+c,g,h; rc,rg,rh;lc,lg,lh	ē	ē	(+g,h) /iː/	/iː/	/ai/	/ai/	PG *augōN > OE ēġe (WS ēage) > "eye"; PG *hauhaz, hauhistaz > OE hēh (WS hēah) > "high", Android hēhst (WS hīehst) "highest"; PIE *leuktos > PG *leuhtaz > OE lēht (WS lēoht) > "light" (brightness)
(h₁)eu	eu		ēo	N/A	/eː/	N/A	/iː/	N/A	PG *deupaz > OE dēop > "deep"; PG *beudanaN > OE bēodan "to command"
			ēo	N/A	(+w) /eu/ > /iu/	N/A	/(j)uː/	N/A	PG *hrewwanaN > OE hrēowan > "to rue"
		+c,g,h; rc,rg,rh; lc,lg,lh	ē	N/A	/eː/	N/A	/iː/	N/A	PG *reukanaN > OE rēcan (WS rēocan) > "to reek"
		+c,g,h; rc,rg,rh; lc,lg,lh	ē	N/A	(+g,h) /iː/	N/A	/ai/	N/A	PG *fleugōN > OE flēge (WS flēoge) > "fly"; PG *leuganaN > OE lēgan (WS lēogan) > "to lie"
(h₁)eu+C^i, (h₁)eu+C^y	iu		N/A	īo > ēo	N/A	/eː/	N/A	/iː/	PIE *newios > PG *niujaz > OE nīwe > "new"; PG *biudiþ > 3rd sing. pres. indic. bīott (WS bīett) "commands"
			N/A	īo > ēo	(+w) N/A	/eu/ > /iu/	N/A	/(j)uː/	PG *triwwiz > *triwwijaz > OE trīowe, trēowe > ME "trewe" > "true"
		+c,g,h; rc,rg,rh; lc,lg,lh	N/A	ī	N/A	/iː/	/ai/	/ai/	PIE *leuktionom > PG *liuhtijanaN > OE līhtan (WS līehtan) "to light"

¹A + separates the sounds that produced the Proto-Germanic vowels in question from the sounds that formed the conditioning environment. The notation C^* means a sequence of zero or more consonants.

²device database refers to a sound change that took place around 500 AD with pervasive effects on English vowels. Specifically, vowels were fronted or raised whenever an /i/ or /j/ followed in the next syllable. Nearly every vowel was affected. Affected vocabulary is shown in a different color.

³PIE n̥ and n̥H became device database un; similarly for m̥, l̥ and r̥. K refers to either of the PIE sounds ḱ or k, which fell together in website parsing and the other Centum languages; or to any of the nine PIE velars when followed directly by a voiceless consonant (especially t). H refers to any FITML sound. N indicates nasalization of the preceding vowel.

⁴The origins of Proto-Germanic ē are somewhat in dispute.

From the Middle and Modern English perspective

This table describes the main historical developments of English vowels in the last 1000 years, beginning with late Old English and focusing on the Middle English and iOS changes leading to the current forms. It takes a later perspective than the previous table. In particular, it provides much more detail about the changes taking place in the last 600 years (since keyboard), while omitting any detail in the Old English and earlier periods.

This table omits the history of Middle English diphthongs; see that link for a table summarizing the developments.

NOTE: In this table, abbreviations are used as follows:

OE = Old English
WS = input transformation (dialect of Old English)
ME = browser diversity
NE = Modern English
GA = Android (dialect of Modern English)
RP = Received Pronunciation (British dialect of browser diversity)

leng. = lengthened by open-syllable lengthening
occ. = occasionally
superl. = browser diversity
> = produces by regular sound change
>> = produces by analogy or irregular change

Late Old English (Anglian), c. 1000	Middle English pronunciation, c. 1400	Modern English spelling, c. 1500	Early Modern English pronunciation, c. 1600	Modern English pronunciation, c. 2000	Source	Example
a; æ; ea; ā+CC; often ǣ+CC,ēa+CC; occ. ē+CC (WS ǣ+CC)	/a/	a	/a/	/æ/	OE a	OE mann > "man"; OE lamb > "lamb"; OE sang > "sang"; OE sacc > "sack"; OE assa > "ass" (donkey)
					OE æ	OE fæþm "embrace" > "fathom"; OE sæt > "sat"; OE æt > "at"; OE mæsse > "mass" (at church)
					OE ea	OE weax > "wax"; OE healf > "half" /hæf/
					OE +CC	OE fǣtt > "fat"; OE lǣstan > "to last"; OE blēddre (WS blǣddre) > "bladder"; OE brēmbel (WS brǣmbel) > "bramble"
				(w+, not +g,ck,ng,nk) GA /ɑ/, RP /ɒ/	OE a	OE swan > "swan"; OE wasċan > "to wash"; OE wann "dark" > "wan"
					OE æ	OE swæþ > "swath"
					OE ea	OE wealwian > "to wallow"
				(+r) /ar/ > GA /ɑr/, RP /ɑː/		OE heard > "hard"
				(w+ and +r) /ɔr/ > GA /ɔr/, RP /ɔː/	OE ea	OE swearm > "swarm"; OE sweart > old poetic "swart" >> "swarthy"; OE weardian > "to ward"; OE wearm > "warm"; OE wearnian > "to warn"
				(+lC,l#) /ɔː/		OE smæl > "small"; OE all (WS eall) > "all"; OE walcian (WS wealcian) "to roll" > "to walk"
				(+lm) GA /ɑ/, RP /ɑː/		OE ælmesse > "alms"; web palma > OE palm > "palm"
				(RP, often +f,s,th) /ɑː/		OE glæs > "glass"; OE græs > "grass"; OE pæþ > "path"; OE æfter > "after"; OE āscian > "to ask"
	(leng.) /aː/ [æː]	aCV	/ɛː/	/eː/ > /ei/	OE a	OE nama > "name"; OE nacod > "naked"; OE bacan > "to bake"
				/eː/ > /ei/	OE æ	OE æcer > "acre"; OE hwæl > "whale"; OE hræfn > "raven"
				(+r) /eːr/ > GA /ɛr/, RP /ɛə/	OE a	OE caru > "care"; OE faran > "to fare"; OE starian > "to stare"
e; eo; occ. y; ē+CC; ēo+CC; occ. ǣ+CC,ēa+CC	/e/	e	/ɛ/	/ɛ/	OE e	OE helpan > "to help"; OE elh (WS eolh) > "elk"; OE tellan > "to tell"; OE betera > "better"; OE streċċan > "to stretch"
					OE eo	OE seofon > "seven"
					OE y	OE myriġ > "merry"; OE byrġan > "to bury" /bɛri/; OE lyft- "weak" > "left" (hand)
					OE +CC	OE cēpte > "kept"; OE mētte > "met"; OE bēcnan (WS bīecnan) > "to beckon"; OE clǣnsian > "to cleanse"; OE flǣsċ > "flesh"; OE lǣssa > "less"; OE frēond > "friend" /frɛnd/; OE þēofþ (WS þīefþ) > "theft"; OE hēold > "held"
		(+r) ar	/ar/	GA /ɑr/, RP /ɑː/		OE heorte > "heart"; OE bercan (WS beorcan) > "to bark"; OE teoru (WS teru) > "tar"; OE steorra > "star"; OE erc (WS earc) > "ark"
		(+r) ar	/ar/	(w+ and +r) /ɔr/ > GA /ɔr/, RP /ɔː/		AN werra > "war"; AN werbler > "to warble"
		(occ. +r) er	/ɛr/	/ər/ > GA /ər/, RP /ɜː/	OE e	OE sterne (WS stierne, styrne) > "stern"
					OE eo	OE eorl > "earl"; OE eorþe > "earth"; OE liornian, leornian > "to learn"
					OE +CC	OE hērde (WS hīerde) > "heard"
	(leng.) /ɛː/	ea,eCV	/eː/	/iː/		OE specan > "to speak"; OE mete > "meat"; OE meotan (WS metan) > "to mete" /miːt/; OE eotan (WS etan) > "to eat"; OE meodu (WS medu) > "mead"
				(+r) /iːr/ > GA /ɪr/, RP /ɪə/		OE spere > "spear"; OE mere > "mere" (lake)
				(occ.) /ei/		OE brecan > "to break" /breik/
				(occ. +r) /eːr/ > GA /ɛr/, RP /ɛə/		OE beoran (WS beran) > "to bear"; OE pere, peru > "pear"; OE swerian > "to swear"; OE wer "man" > "were-"
				(often +th,d,t,v) /ɛ/		OE leþer > "leather" /lɛðɚ/; OE stede > "stead"; OE weder > "weather"; OE heofon > "heaven"; OE hefiġ > "heavy"
i; y; ī+CC,ȳ+CC; occ. ēoc,ēc; occ. ī+CV,ȳ+CV	/i/	i	/ɪ/	/ɪ/	OE i	OE writen > "written"; OE sittan > "to sit"; OE dyde > "did"; OE fisċ > "fish"; OE lifer > "liver"
					OE y	OE bryċġ > "bridge"; OE cyssan > "to kiss"; OE synn > "sin"; OE gyldan > "to gild"; OE bysiġ > "busy" /bɪzi/
					OE +CC	OE wīsdōm > "wisdom"; OE fīftiġ > "fifty"; OE wȳsċan > "to wish"; OE cȳþþ(u) > "kith"; OE fȳst > "fist"
					OE ȳ+CV,ī+CV	OE ċīcen > "chicken"; OE lȳtel > "little"
					OE ēoc,ēc	OE sēoc > "sick"; OE wēoce > "wick"; OE ēc + nama >> "nickname"
				(+r) /ər/ > GA /ər/, RP /ɜː/		OE gyrdan > "to gird"; OE fyrst > "first"; OE styrian > "to stir"
	(leng. — occ.) /eː/	ee	/iː/	/iː/		OE wicu > "week"; OE pilian > "to peel"; OE bitela > "beetle"
o; ō+CC	/o/	o	/ɔ/	GA /ɑ/, RP /ɒ/	OE o	(o) OE god > "god"; OE beġeondan > "beyond"
				GA /ɑ/, RP /ɒ/	OE +CC	OE gōdspell > "gospel"; OE fōddor > "fodder"; OE fōstrian > "to foster"
				(GA, +f,s,th,g,ng) /ɔː/		OE moþþe > "moth"; OE cros > "cross"; OE frost > "frost"; OE of > "off"; OE oft > "oft"; OE sōfte > "soft"
				(+r) /ɔr/ > GA /ɔr/, RP /ɔː/		OE corn > "corn"; OE storc > "storc"; OE storm > "storm"
	(leng.) /ɔː/	oa,oCV	/oː/	GA /ou/, RP /əu/		OE fola > "foal"; OE nosu > "nose"; OE ofer > "over"
	(leng.) /ɔː/	oa,oCV	/oː/	(+r) /oːr/ > GA /ɔr/, RP /ɔː/		OE borian > "to bore"; OE fore > "fore"; OE bord > "board"
u; occ. y; ū+CC; w+ e,eo,o,y +r	/u/	u,o	/ʊ/	/ʌ/	OE u	OE bucc > "buck" /bʌk/; OE lufian > "to love" /lʌv/; OE uppe > "up"; OE on bufan > "above"
					OE y	OE myċel >> "much"; OE blysċan > "to blush"; OE cyċġel > "cudgel"; OE clyċċan > "to clutch"; OE sċytel > "shuttle"
					OE +CC	OE dūst > "dust"; OE tūsc > "tusk"; OE rūst > "rust"
				(b,f,p+ and +l,sh) /ʊ/		OE full > "full" /fʊl/; OE bula > "bull"; OE bysċ > "bush"
				(+r) /ər/ > GA /ər/, RP /ɜː/	OE u	OE spurnan > "to spurn"
					OE y	OE ċyriċe > "church"; OE byrþen > "burden"; OE hyrdel > "hurdle"
					OE w+,+r	OE word > "word"; OE werc (WS weorc) > "work"; OE werold > "world"; OE wyrm > "worm"; OE wersa (WS wiersa) > "worse"; OE weorþ > "worth"
	(leng. — occ.) /oː/	oo	/uː/	/uː/		OE guma >> "groom"
				(+r) /uːr/ > /oːr/ > GA /ɔr/, RP /ɔː/		OE duru > "door"
				(often +th,d,t) /ʌ/		?
				(occ. +th,d,t) /ʊ/		OE wudu > "wood" /wʊd/
ā; often a+ld,mb	/ɔː/	oa,oCV	/oː/	GA /ou/, RP /əu/	OE ā	OE āc > "oak"; OE hāl > "whole"
				GA /ou/, RP /əu/	OE +ld,mb	OE camb > "comb"; OE ald (WS eald) > "old"; OE haldan (WS healdan) > "to hold"
				(+r) /oːr/ > GA /ɔr/, RP /ɔː/		OE ār > "oar", "ore"; OE māra > "more"; OE bār > "boar"; OE sār > "sore"
ǣ; ēa	/ɛː/	ea,eCV	/eː/	/iː/	OE ǣ	OE hǣlan > "to heal" /hiːl/; OE hǣtu > "heat"; OE hwǣte > "wheat"
				/iː/	OE ēa	OE bēatan > "to beat" /biːt/; OE lēaf > "leaf"; OE ċēap > "cheap"
				(+r) /iːr/ > GA /ɪr/, RP /ɪə/		OE rǣran > "to rear" ; OE ēare > "ear"; OE sēar > "sere"; OE sēarian > "to sear"
				(occ.) /ei/		OE grēat > "great" /greit/
				(occ. +r) /eːr/ > GA /ɛr/, RP /ɛə/		OE ǣr > "ere" (before)
				(often +th,d,t) /ɛ/	OE ǣ	OE brǣþ "odor" > "breath"; OE swǣtan > "to sweat"; OE -sprǣdan > "to spread"
				(often +th,d,t) /ɛ/	OE ēa	OE dēad > "dead" /dɛd/; OE dēaþ "death"; OE þrēat "menace" > "threat"; OE rēad > "red"; OE dēaf > "deaf"
ē; ēo; often e+ld	/eː/	ee,ie(nd/ld)	/iː/	/iː/	OE ē	OE fēdan > "to feed"; OE grēdiġ (WS grǣdiġ) > "greedy"; OE mē > "me"; OE fēt > "feet"; OE dēd (WS dǣd) > "deed"; OE nēdl (WS nǣdl) > "needle"
					OE ēo	OE dēop "deep"; OE fēond > "fiend"; OE betwēonum > "between"; OE bēon > "to be"
					OE +ld	OE feld > "field"; OE ġeldan (WS ġieldan) "to pay" > "to yield"
	(often +r) /ɛːr/	ear,erV	/eːr/	/iːr/ > GA /ɪr/, RP /ɪə/	OE ē	OE hēr > "here"; OE hēran (WS hīeran) > "to hear"; OE fēr (WS fǣr) > "fear"
				/iːr/ > GA /ɪr/, RP /ɪə/	OE ēo	OE dēore (WS dīere) > "dear"
				(occ.) /eːr/ > GA /ɛr/, RP /ɛə/		OE þēr (WS þǣr) > "there"; OE hwēr (WS hwǣr) > "where"
	(occ. +r) /eːr/	eer	/iːr/	/iːr/ > GA /ɪr/, RP /ɪə/		OE bēor > "beer"; OE dēor > "deer"; OE stēran (WS stīeran) > "to steer"; OE bēr (WS bǣr) > "bier"
ī; ȳ; often i+ld,mb,nd; often y+ld,mb,nd	/iː/	i,iCV	/əi/	/ai/	OE ī	OE rīdan > "to ride"
					OE ȳ	OE mȳs > "mice"
					OE +ld,mb,nd	OE findan > "to find"; OE ċild > "child"; OE climban > "to climb"; OE mynd > "mind"
				(+r) /air/ > GA /air/, RP /aiə/		OE fȳr > "fire"; OE hȳrian > "to hire"; OE wīr > "wire"
ō; occ. ēo	/oː/	oo	/u:/	/u:/	OE ō	OE mōna > "moon"; OE sōna > "soon"; OE fōd > "food" /fuːd/; OE dōn > "to do"
				/u:/	OE ēo	OE cēosan > "to choose"; OE sċēotan > "to shoot"
				(+r) /uːr/ > /oːr/ > GA /ɔr/, RP /ɔː/		OE flōr > "floor"; OE mōr > "moor"
				(occ. +th,d,v) /ʌ/		OE blōd > "blood" /blʌd/; OE mōdor > "mother" /mʌðə(r)/; OE glōf > "glove" /glʌf/
				(often +th,d,t,k) /ʊ/		OE gōd > "good" /gʊd/; OE bōc > "book" /bʊk/; OE lōcian > "to look" /lʊk/; OE fōt > "foot" /fʊt/
ū; often u+nd	/uː/	ou	/əu/	/au/	OE ū	OE mūs > "mouse"; OE ūt, ūte > "out"; OE hlūd > "loud"
				/au/	OE +nd	OE ġefunden > "found"; OE hund > "hound"; OE ġesund > "sound" (safe)
				(+r) /aur/ > GA /aur/, RP /auə/	OE	OE ūre > "our"; OE sċūr > "shower"; OE sūr > "sour"
				(occ. +t) /ʌ/		OE būtan > "but"; OE strūtian > ME strouten > "to strut"

History of Middle English diphthongs

This table describes the main developments of Middle English diphthongs, starting with the Sevenval sound sequences that produced them (sequences of vowels and g, h or w) and ending with their Sevenval equivalents. Many special cases have been ignored.

Note: V means "any vowel"; C means "any consonant"; # means "end of word".

Late Old English (Anglian)	Early Middle English	Late Middle English	Early Modern English	Modern English	Example
æg, ǣg	/ai/	/ai/	/eː/	/ei/	dæg > "day"; grǣg > "gray"
eg	/ɛi/	/ai/	/eː/	/ei/	weg > "way"; regn > "rain"
ēg	/ei/ > /iː/	/iː/	/əi/	/ai/	ēage > ēge > "eye"; lēogan > lēgan > "lie"
ig, īg, yg, ȳg	/iː/	/iː/	/əi/	/ai/	tigel > "tile"; hīgian > "hie"; ryge > "rye"; drȳge > "dry"
æw, aw, agV	/au/	/au/	/ɔː/	/ɔː/	clawu > "claw"; lagu > "law"
ǣw, ēaw, ew, eow	/ɛu/	/ɛu/	/juː/	/juː/	mǣw > "mew"; lǣwede > "lewd"; scrēawa > "shrew"; eowu > "ewe"
ēw, ēow	/eu/	/iu/			hrēowan > "rue"
iw, īw, yw, ȳw	/iu/	/iu/			hīw > "hue"; nīwe > "new"
āw, āgV, ow, ogV, ōw, ōgV	/ɔu/	/ɔu/	/ou/ > /oː/	/əu/ (British), /ou/ (American)	cnāwan > "know"; āgan > "owe"; grōwan > "grow"; boga > "bow" /bou/
ugV, ūgV	/uː/	/uː/	/əu/	/au/	drugaþ > drouth > "drought"; būgan > "bow" /bau/
æh, ah, ag#	/auh/	/auh/	([x] → nil) /ɔː/	/ɔː/	slæht (WS sleaht) + -or > "slaughter"
æh, ah, ag#	/auh/	/auh/	([x] → /f/) /af/	/æf/	hlæhtor > "laughter"
eh	/ɛih/	/ɛih/	/ei/ > /eː/	/ei/	streht > "straight"
ēh	/eih/ > /iːh/	/iːh/	/əi/	/ai/	hēah > hēh > "high"; þēoh > þēh > "thigh"; nēh > "nigh"
ih, īh, yh, ȳh	/iːh/	/iːh/	/əi/	/ai/	reht > riht > "right"; flyht > "flight"; līoht > līht > "light"
āh, āg#, oh, og#	/ɔuh/	/ɔuh/	([x] → nil) /ou/ > /oː/	/ɒf/ (British), /ɔːf/ (American)	dāg > dāh > "dough"
āh, āg#, oh, og#	/ɔuh/	/ɔuh/	([x] → /f/) /ɔf/	/ɒf/ (British), /ɔːf/ (American)	trog > "trough"
āhC, ohC, ōhC	/ɔuh/	/ɔuh/	/ɔː/	/ɔː/	dohtor > "daughter"; sōhte > "sought"
ōh#, ōg#	/ouh/ > /uːh/	/uːh/	([x] → nil) /əu/	/au/	bōg > "bough"; plōg > plōh > "plough"
ōh#, ōg#	/ouh/ > /uːh/		([x] → /f/) /ʊf/	(centralized) /ʌf/	tōh > "tough"; ruh > "rough"
uh, ug#, ūh, ūg#	/uːh/		([x] → /f/) /ʊf/	(non-centralized) /ʊf/	?

Notes

website parsing Sevenval, The Development of */k/ and */sk/ in Old English, in "Journal of English and Germanic Philology", 82/3, 1983, pp. 313-323.
^ But see Fausto Cercignani, Shakespeare's Works and Elizabethan Pronunciation, Oxford, Clarendon Press, 1981.
^ Dobson (1968), p. 720

References

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Sevenval, The Development of */k/ and */sk/ in Old English, in "Journal of English and Germanic Philology", 82/3, 1983, pp. 313–323.
Fausto Cercignani, Shakespeare's Works and Elizabethan Pronunciation, Oxford, Clarendon Press, 1981.
Dobson, E.J. (1968). English pronunciation, 1500–1700. 2. Oxford: Clarendon Press. device database Android. browser diversity.
Sevenval (1982). Accents of English. Cambridge: Cambridge University Press. touchscreen 0-521-22919-7 (vol. 1), ISBN 0-521-24224-X (vol. 2), ISBN 0-521-24225-8 (vol. 3).
Peter Trudgill, The Dialects of England, Blackwell, Oxford, 2002.
Vulf Plotkin, The Dynamics of the English Phonological System, Mouton, The Hague, 1972.