Phonological history of English consonant clusters

The phonological history of the English language includes various changes in the phonology of consonant clusters.
H-cluster reductions.
The H-cluster reductions are various consonant reductions that have occurred in the history of English, involving consonant clusters beginning with that have lost the (or become reduced to ) in some or all dialects.
Reductions of /hw/.
The cluster (spelled ⟨wh⟩ since Middle English) has been subject to two kinds of reduction:
Reduction of /hl/, /hr/ and /hn/.
The Old English consonant clusters , and were reduced to , , and in Middle English. For example, Old English , and become "loaf", "ring" and "nut" in Modern English.
Reduction of /hj/.
In some dialects of English the cluster is reduced to , leading to pronunciations like for "huge" and for "human", and making "hew" a homophone of "ewe" and "you". This is sometimes considered a type of glide cluster reduction, but it is much less widespread than wh-reduction, and is generally stigmatized where it is found. Aside from accents with general H-dropping, in the United States this reduction is mostly found in accents of Philadelphia and New York City; it also occurs in Cork accents of Irish English. In other dialects of English, "hew" and "yew" remain distinct; however, the cluster of "hew", "human", etc. is often reduced from to just (a voiceless palatal fricative).
Y-cluster reductions.
Y-cluster reductions are reductions of clusters ending with the palatal approximant , which is the sound of in "yes", and is sometimes referred to as "yod", from the Hebrew letter yod(h), which has the sound . Many such clusters arose in dialects in which the falling diphthong (the product of the merger of several Middle English vowel sequences) became the rising diphthong . (For more information, see Phonological history of English high back vowels.) They were thus often found before the vowel , as in "cube" – which was in some cases modified to or before (historical) , as in "cure", or weakened to or as in "argument". They also occurred in words ending in "-ion" and "-ious", such as "nation" and "precious".
This change from to , which had occurred in London by the end of the 17th century, did not take place in all dialects. A few dialects, notably in Wales, as well as in some parts of northern England, New England, and the American South, still retain a (falling) diphthong where standard English has – these dialects therefore lack the clusters with and have not been subject to the reductions described here.
The diphthongs or are most commonly indicated by the spellings "eu", "ew", "uCV" (where "C" is any consonant and "V" is any vowel), "ue" and "ui", as in "feud", "few", "mute", "cue" and "suit", while the historical monophthong is commonly indicated by the spellings "oo" and "ou", as in "moon" and "soup".
Yod-dropping.
Yod-dropping is the elision of the from certain syllable-initial clusters of the type described above. Particular cases of yod-dropping may affect all or some of the dialects that have the relevant clusters.
The change of to in these positions (as described above) produced some clusters which would have been difficult or impossible to pronounce, which led to what John Wells calls Early Yod Dropping in which the was elided in the following environments:
The previously mentioned accents that did not have the → change were not subject to this process. Thus, for example, in much Welsh English pairs like "chews"/"choose", "yew"/"you" and "threw"/"through" remain distinct: the first member of each pair has the diphthong , while the second member has :
Conversely, an initial does not appear in Welsh English before in words such as "yeast" and "yield".
Many varieties of English have extended yod-dropping to the following environments if the is in the same syllable as the preceding consonant:
Yod-dropping in the above environments used to be considered nonstandard in England but now also occurs by educated RP-speakers. (The after is not normally dropped in RP in medial positions, however: compare "pursuit" .) In General American, yod-dropping is found not only in the above environments but also after , and , for example "tune" , "dew" , "new" 
The lack of yod-dropping in those contexts has occasionally been held to be a shibboleth distinguishing Canadians from Americans. However, in a survey conducted in the Golden Horseshoe area of [Southern Ontario] in 1994, over 80% of respondents under the age of 40 pronounced "student" and "news" without yod.
General American thus undergoes yod-dropping after all alveolar consonants. A few accents of American English, such as working-class Southern American English, however, preserve the distinction in pairs like "do"/"dew" because like in the Welsh English dialects discussed above, they retain a diphthong in words in which RP has : , , etc.
However, in words like "annual", "menu", "volume", "Matthew", "continue", etc., with a syllable break before the , there is no yod-dropping. The same applies accordingly to British and other accents; the yod is often dropped after initial , for example, but it is not dropped in words like "volume" or "value". (British speakers omit the in "figure", but most Americans retain it.)
Yod-dropping after , , and was also a traditional feature of Cockney speech, which continues to be the case after , but now, after and , yod-coalescence is now more common.
Some East Anglian accents such as Norfolk dialect extend yod-dropping not only to the position after , or but also to the position after nonalveolar consonants as well: pairs like "beauty"/"booty", "mute"/"moot", "cute"/"coot" can then be homophonous. A well-known series of British television advertisements beginning in the 1980s featured Bernard Matthews, who was from Norfolk and described his turkeys as "bootiful" (for "beautiful"). Such accents pronounce a in words like "use", "unit", etc. only if there is no consonant before the .
Yod-coalescence.
Yod-coalescence is a process that fuses the clusters into the sibilants respectively (for the meanings of those symbols, see English phonology). The first two are examples of affrication.
Unlike yod-dropping, yod-coalescence frequently occurs with clusters that would be considered to span a syllable boundary and so commonly occurs before unstressed syllables. For example, in "educate", the cluster would not usually be subject to yod-dropping in General American, as the is assigned to the previous syllable, but it commonly coalesces to . Here are a few examples of yod-coalescence universal in all English dialects:
In some other words, the coalesced pronunciation is common in English dialects around the world, but an older non-coalesced form still exists among some speakers of standard British English:
Coalescence can even occur across word boundaries, as in the colloquial "gotcha" (for "got you" ) and "whatcha" (for "what're you" ).
In certain English accents, yod-coalescence also occurs in stressed syllables, as in "tune" and "dune". That occurs only in Australian, Cockney, Estuary English, Zimbabwean English, some speakers of Hiberno-English, Newfoundland English, South African English, and to a certain extent in New Zealand English, many speakers in Scottish English, and even some varieties of English in Asia, like Philippine English (many speakers because of the influence by the phonology of their mother languages). That results in pronunciations such as the following:
In certain varieties such as Australian and Ugandan English, stressed can also coalesce:
That can lead to additional homophony; for instance, "dew" and "due" come to be pronounced the same as "Jew".
Yod-coalescence has traditionally been resisted in Received Pronunciation. It has certainly become established in words of the first group listed above ("nature", "soldier", "pressure" etc.), but it is not yet universal in those of the second group ("educate" etc.), and it does not generally occur in those of the third group ("dew", "tune" etc.).
See also
Other initial cluster reductions.
Reduction of /wr/ and /wl/.
Old and Middle English had an initial cluster, hence the spelling of words like "write" and "wrong". This was reduced to just , apparently during the 17th century. An intermediate stage may have been an with lip rounding.
As a result of this reduction, pairs of words like "rap" and "wrap", "rite" and "write", etc. are homophones in practically all varieties of Modern English. They remain distinct in the Doric dialect of Scots, where the "wr-" cluster is pronounced .
Old English also had a cluster , which reduced to during Middle English. For example, the word "lisp" derives from Old English "wlisp(ian)".
Reduction of.
Middle English initial is reduced in modern English to , making pairs like "knot/not" and "knight/night" homophones.
The cluster was spelled "cn-" in Old English; this changed to "kn-" in Middle English, and this spelling survives in Modern English, despite the loss of the sound. Cognates in other Germanic languages usually still sound the initial . For example, the Old English ancestor of "knee" was "cnēo", pronounced , and the cognate word in Modern German is "Knie", pronounced .
Most dialects of English reduced the initial cluster to relatively recently; the change seems to have taken place in educated English during the seventeenth century. The cluster is preserved in some Scots dialects.
Reduction of /ɡn/.
The Middle English initial cluster is reduced to in Modern English. Like the reduction of , this seems to have taken place during the seventeenth century. The change affected words like "gnat", "gnostic", "gnome", etc., the spelling with "gn-" being retained despite the loss of the sound. The cluster is preserved in some Scots dialects.
The song "The Gnu" jokes about this silent "g" and other silent letters in English. In fact the "g" in "gnu" may always have been silent in English, since this loanword did not enter the language until the late 18th century. The trumpeter Kenny Wheeler wrote a composition titled "Gnu High", a pun on "new high".
S-cluster reductions.
In some types of Caribbean English, the initial clusters , , and are reduced by the loss of . The following stop is then subject to regular aspiration (or devoicing of the following approximant) in its new word-initial environment. Some examples of such pronunciations are:
According to Wells, these reductions occur only in the broadest creole.
Final cluster reductions.
NG-coalescence.
NG-coalescence is a historical sound change by which the final cluster , pronounced (the being realized as a velar nasal by assimilation with the velar ), came to be pronounced as just – that is, the final was dropped, but the velar quality of the nasal remained. The change took place in educated London speech around the end of the 16th century, and explains why there is no sound at the end of words like "fang", "sing", "wrong" and "tongue" in the standard varieties of Modern English.
The change in fact applies not only at the end of a word, but generally at the end of a morpheme. If a word ending in "-ng" is followed by a suffix or is compounded with another word, the pronunciation normally remains. For example, in the words "fangs", "sings", "singing", "singer", "wronged", "wrongly", "hangman", there is no sound. An exception is the comparative and superlative forms of adjectives: in the words "longer/longest", "stronger/strongest", "younger/youngest", the is pronounced in most accents. The pronunciation with is thus possible only before a vowel; before a consonant, the only possibility is a bare .
In other cases (when it is not morpheme-final), word-internal "-ng-" does not show the effects of coalescence, and the pronunciation is retained, as in "finger" and "angle". This means that the words "finger" and "singer" do not rhyme in most modern varieties of English, although they did in Middle English. The process of NG-coalescence might therefore be referred to as the "singer–finger split".
Some accents, however, do not show the full effects of NG-coalescence as described above, and in these accents "sing" may be found with , the suffix "-ing" may be pronounced (though G-dropping is another possibility), and "singer" may rhyme with "finger". This is particularly associated with English English accents in an area of Northern England (especially Lancashire), the West Midlands and Derbyshire in the East Midlands, and is also present in north-east varieties of Welsh English. This includes the cities of Birmingham (see Brummie), Manchester, Liverpool (see Scouse), Sheffield and Stoke-on-Trent. It is also associated with some American English accents in the New York City area.
On the other hand, in some accents of the west of Scotland and Ulster, NG-coalescence is extended to morpheme-internal position, so that "finger" is pronounced (cf. Dutch "vinger" ), thus rhyming with "singer" (although the is not dropped before a stressed syllable, as in "engage").
It is because of NG-coalescence that is now normally regarded one of the phonemes of standard English. In Middle English, the can be regarded as an allophone of , occurring before velar consonants, but in Modern English, in view of minimal pairs such as "pan–pang" and "sin–sing", that analysis no longer appears to hold. Nevertheless, some linguists (particularly generativists) do regard a word like "sing" as being underlyingly , positing a rule that deletes after a nasal before a morpheme boundary, after the nasal has undergone assimilation. A problem with this view is that there are a few words in which is followed neither by a velar nor a morpheme boundary (such as "gingham", "dinghy", "orangutan" and "Singapore" for those speakers who pronounce them without ), and some in which the is not deleted before a morpheme boundary ("longer" etc., as noted above).
The above-mentioned accents which lack NG-coalescence may more easily be analyzed as lacking a phoneme . The same may apply to those where NG-coalescence is extended to morpheme-internal position, since here a more consistent -deletion rule can be formulated.
G-dropping.
G-dropping is a popular name for the feature of speech whereby is used in place of the standard in weak syllables. This applies especially to the "-ing" ending of verbs, but also in other words such as "morning", "nothing", "ceiling", "Buckingham", etc. G-dropping speakers may pronounce this syllable as or (reducing to a syllabic [n] in some cases), while non-G-dropping speakers have ( with the weak vowel merger) or .
Relative to the great majority of modern dialects, which have NG-coalescence, G-dropping does not involve the dropping of any sound, simply the replacement of the velar nasal with the alveolar nasal. The name derives from the apparent orthographic consequence of replacing the sound written with that normally written . The spelling "-in' " is sometimes used to indicate that a speaker uses the G-dropping pronunciation, as in "makin' " for "making".
The pronunciation with rather than is a long-established one. Old English verbs had a present participle in "-ende" and a verbal noun (gerund) form in "-ing(e)". These merged into a single form, written "-ing", but not necessarily spoken as such – the pronunciation may be inherited from the former distinct present participle form. The variant appears to have been fashionable generally during the 18th century, with the alternative being adopted in educated speech around the 1820s, possibly as a spelling pronunciation.
Today, G-dropping is a feature of colloquial and non-standard speech of all regions, including stereotypically of Cockney, Southern American English and African American Vernacular English. Its use is highly correlated with the socioeconomic class of the speaker, with speakers of lower classes using with greater frequency. It has also been found to be more common among men than women, and less common in more formal styles of speech.
The fact that the pronunciation was formerly associated with certain upper-class speech is reflected in the phrase "huntin’, shootin’ and fishin’" (used in referring to country gentry who frequently engaged in such field sports). Further evidence that this pronunciation was once standard comes from old rhymes, as in this couplet from John Gay's 1732 pastoral "Acis and Galatea", set to music by Handel:
 was presumably pronounced "shepherd, what art thou pursuin', heedless runnin' to thy ruin", although this would sound very odd in an opera today. Similarly, in the poetry of Jonathan Swift (1667–1745), "-ing" forms consistently rhyme with words ending in , as in this verse of "A Ballad on the Game of Traffic", where "lining" rhymes with "fine in":
Reduction of /mb/ and /mn/.
In later Middle English, the final cluster was reduced to just (the plum-plumb merger). This affects words such as "lamb" and "plumb", as well as derived forms with suffixes, such as "lambs", "lambing", "plumbed", "plumber".
By analogy with words like these, certain other words ending in , which had no historical sound, had a silent letter added to their spelling by way of hypercorrection. Such words include "limb" and "crumb".
Where the final cluster occurred, this was reduced to (the him-hymn merger), as in "column", "autumn", "damn", "solemn". (Compare French , where the cluster has been reduced to .) Both sounds are nonetheless still pronounced before vowels in certain derivatives, such as "autumnal", "damnation", "solemnity".
Generalized final cluster reduction.
General reduction of final consonant clusters occurs in African American Vernacular English and Caribbean English. The new final consonant may be slightly lengthened as an effect.
Examples are:
The plurals of "test" and "desk" may become "tesses" and "desses" by the same rule that gives plural "messes" from singular "mess".
Medial cluster reductions.
When a consonant cluster ending in a stop is followed by another consonant or cluster in the next syllable, the final stop in the first syllable is often elided. This may happen within words or across word boundaries. Examples of stops that will often be elided in this way include the in "postman" and the in "cold cuts" or "band saw".
Historically, similar reductions have taken place before syllabic consonants in certain words, leading to the silent in words like "castle" and "listen". This change took place around the 17th century. In the word "often", the sound later came to be re-inserted by some speakers as a spelling pronunciation.
An earlier reduction that took place in early Middle English was the change of to (the sent-cent merger). This led to the modern sound of soft.
Consonant insertions.
Prince–prints merger.
For many speakers, an epenthetic is inserted in the final cluster , making it identical or very similar to the cluster . For example, the words "prince" and "prints" have come to be homophones or nearly so.
The epenthesis is a natural consequence of the transition from the nasal to the fricative ; if the raising of the soft palate (which converts a nasal to an oral sound) is completed before the release of the tongue tip (which enables a fricative sound), an intervening stop naturally results. The merger of and is not necessarily complete, however; the duration of the epenthetic in has been found to be often shorter (and the longer) than in the underlying cluster . Some speakers preserve a clearer distinction, with "prince" having , and "prints" having or . The epenthesis does not occur between syllables, in words like "consider".
Other insertions.
The merger of and is also possible, making "bans" and "pens" sound like "bands" and "pends". However, this is less common than the merger of and described above, and in rapid speech may involve the elision of the from rather than epenthesis in .
Epenthesis of a stop between a nasal and a fricative can also occur in other environments, for example: 
An epenthetic often intervenes in the cluster in the word "dreamt", making it rhyme with "attempt".
Some originally epenthetic consonants have become part of the established pronunciation of words. This applies, for instance, to the in words like "thimble", "grumble" and "scramble".
For the insertion of glottal stops before certain consonants, see Glottalization below.
Alterations of clusters.
Assimilation.
In English as in other languages, assimilation of adjacent consonants is common, particularly of a nasal with a following consonant. This can occur within or between words. For example, the in "encase" is often pronounced (becoming a velar nasal by way of assimilation with the following velar stop ), and the in "ten men" likely becomes , assimilating with the following bilabial nasal . Other cases of assimilation also occur, such as pronunciation of the in "bad boy" as . Voicing assimilation determines the sound of the endings "-s" (as in plurals, possessives and verb forms) and "-ed" (in verb forms): these are voiced (, ) following a voiced consonant (or vowel), but voiceless (, ) after a voiceless consonant, as in "gets", "knocked".
Glottalization.
While there are many accents (such as Cockney) in which syllable-final is frequently glottalized (realized as a glottal stop, ) regardless of what follows it, the glottaling of in clusters is a feature even of standard accents, such as RP. There, may be heard for in such words and phrases as "quite good", "quite nice", "nights". More precisely, it occurs in RP when appears in the syllable coda, is preceded by a vowel, liquid or nasal, and it is followed by another consonant except (normally) a liquid or semivowel in the same word, as in "mattress".
Another possibility is pre-glottalization (or glottal reinforcement), where a glottal stop is inserted before a syllable-final stop, rather than replacing it. That can happen before , and or also before the affricate . It can occur in RP in the same environments as those mentioned above, without the final restriction so a glottal stop may appear before the , as in "mattress". It can also occur before a pause as in "quite!" spoken alone but not in "quite easy". In the case of , pre-glottalization is common even before a vowel, as in "teacher".
According to Wells, this pre-glottalization originated in the 20th century (at least, it was not recorded until then). Glottalization of spread rapidly during the 20th century.
S-cluster metathesis.
Final consonant clusters starting with sometimes undergo metathesis, meaning that the order of the consonants is switched. For example, the word "ask" may be pronounced like "ax", with the and the switched.
This example has a long history: the Old English verb "áscian" also appeared as "acsian", and both forms continued into Middle English, the latter, metathesizing to "ask". The form "axe" appears in Chaucer: "I axe, why the fyfte man Was nought housband to the Samaritan?" ("Wife of Bath's Prologue", 1386), and was considered acceptable in literary English until about 1600. It persists in some dialects of rural England as well as in Ulster Scots as , and in Jamaican English as , from where it has entered London speech as .
S-cluster metathesis has been observed in some forms of African American Vernacular English, although it is not universal, one of the most stigmatized features of AAVE and often commented on by teachers. Examples of possible AAVE pronunciations include:
Merger of /str/ and /skr/.
For some speakers of African American Vernacular English, the consonant cluster is pronounced as . For example, the word "street" may be pronounced as .
The form has been found to occur in Gullah and in the speech of some young African Americans born in the Southern United States. It is reported to be a highly stigmatized feature, with children who use it often being referred to speech pathologists.
Yod-rhotacization.
Yod-rhotacization is a process that occurs for some Memphis AAVE speakers, where is rhotacized to in consonant clusters, causing pronunciations like:
Compare yod-dropping and yod-coalescence, described above (and also the coil–curl merger, which features the reverse process, → ).