Phonological history of English close front vowels

The close and mid-height front vowels of English have undergone a variety of changes over time and often vary by dialect.

Developments involving long vowels

Merger of with and with

had the two vowel pairs and . By Middle English, the distinction in quality collapsed, leaving only the short–long pair, which became KIT and PRICE in Modern English. Changes in spelling mean that and are not a good indicators of the Old English distinction between the four sounds. For example, Modern English bridge derives from Old English bryċġ, while Modern English scythe derives from Old English sīþe. The name of the letter acquired an initial sound in it to keep it distinct from the name of the letter.

Until Great Vowel Shift

had a long close front vowel, and two long mid front vowels: the close-mid and the open-mid. The three vowels generally correspond to the modern spellings, and respectively, but other spellings are also possible. The spellings that became established in Early Modern English are mostly still used today, but the qualities of the sounds have changed significantly.
The and generally corresponded to similar Old English vowels, and came from Old English or. For other possible histories, see English historical vowel correspondences. In particular, the long vowels sometimes arose from short vowels by Middle English open syllable lengthening or other processes. For example, team comes from an originally-long Old English vowel, and eat comes from an originally-short vowel that underwent lengthening. The distinction between both groups of words is still preserved in a few dialects, as is noted in the following section.
Middle English was shortened in certain words. Both long and short forms of such words often existed alongside each other during Middle English. In Modern English, the short form has generally become standard, but the spelling reflects the formerly-longer pronunciation. The words that were affected include several ending in d, such as bread, head, spread, and various others, including breath, weather, and threat. For example, bread was in earlier Middle English but came to be shortened and to be rhymed with bed.
During the Great Vowel Shift, the normal outcome of was a diphthong, which developed into Modern English, as in mine and find. Meanwhile, became, as in feed, and of words like meat became, which later merged with in nearly all dialects, as is described in the following section.

''Meet–meat'' merger

The meet–meat merger or the merger is the merger of the Early Modern English vowel into the vowel . The merger was complete in standard accents of English by about 1700.
As noted in the previous section, the Early Modern/New English vowel developed from Middle English via the Great Vowel Shift, and ENE was usually the result of Middle English . The merger saw ENE raised further to become identical to and so Middle English and have become in standard Modern English, and meat and meet are now homophones. The merger did not affect the words in which had undergone shortening, and a handful of other words also escaped the merger in the standard accents and so acquired the same vowel as brake, stake, grate. Hence, the words meat, threat, and great now have three different vowels although all three words once rhymed.
The merger results in the lexical set, as defined by John Wells. Words in the set that had ENE are mostly spelled , with a single in monosyllables or followed by a single consonant and a vowel letter, sometimes or , or irregularly. Most of those that had ENE are spelled , but some borrowed words have a single ,, or otherwise. There are also some loanwords in which is spelled , most of which entered the language later.
There are still some dialects in the British Isles that do not have the merger. Some speakers in Northern England have or in the first group of words but in the second group. In Staffordshire, the distinction might rather be between in the first group and in the second group. In some varieties of Irish English, the first group has, and the second preserves. A similar contrast has been reported in parts of Southern and Western England, but it is now rarely encountered there.
In some Yorkshire dialects, an additional distinction may be preserved within the meat set. Words that originally had long vowels, such as team and cream, may have, and those that had an original short vowel, which underwent open syllable lengthening in Middle English, like eat and meat, have a sound resembling, similar to the sound that is heard in some dialects in words like eight and weight that lost a velar fricative.
In Alexander's book about the traditional Sheffield dialect, the spelling "eigh" is used for the vowel of eat and meat, but "eea" is used for the vowel of team and cream. However, a 1999 survey in Sheffield found the pronunciation to be almost extinct there.

Changes before and

In certain accents, when the vowel was followed by, it acquired a laxer pronunciation. In General American, words like near and beer now have the sequence, and nearer rhymes with mirror. In Received Pronunciation, a diphthong has developed and so beer and near are and, and nearer remains distinct from mirror. Several pronunciations are found in other accents, but outside North America, the nearer–''mirror opposition is always preserved. For example, some conservative accents in Northern England have the sequence in words like near, with the schwa disappearing before a pronounced, as in serious.
Another development is that bisyllabic may become smoothed to the diphthong in certain words, which leads to pronunciations like, and for vehicle, theatre/theater and idea, respectively. That is not restricted to any variety of English. It happens in both British English and American English as well as other varieties although it is far more common for Britons. The words that have may vary depending on dialect. Dialects that have the smoothing usually also have the diphthong in words like beer, deer, and fear, and the smoothing causes idea, Korea'', etc. to rhyme with those words.

Other changes

In Geordie, the vowel undergoes an allophonic split, with the monophthong being used in morphologically-closed syllables and the diphthong being used in morphologically-open syllables not only word-finally but also word-internally at the end of a morpheme.
Most dialects of English turn into a diphthong, and the monophthongal is in free variation with the diphthongal , particularly word-internally. However, diphthongs are more common word-finally.
Compare the identical development of the close back vowel.

Developments involving short vowels

Lowering

short has developed into a lax near-close near-front unrounded vowel,, in Modern English, as found in words like kit. According to Roger Lass, the laxing occurred in the 17th century, but other linguists have suggested that it took place potentially much earlier.
The short mid vowels have also undergone lowering and so the continuation of Middle English now has a quality closer to in most accents. Again, however, it is not clear whether the vowel already had a lower value in Middle English.

''Pin''–''pen'' merger

The pin–''pen merger is a conditional merger of and before the nasal consonants,, and. The merged vowel is usually closer to than to. Examples of homophones resulting from the merger include pin–pen, kin–ken and him–hem. The merger is widespread in Southern American English and is also found in many speakers in the Midland region immediately north of the South and in areas settled by migrants from Oklahoma and Texas who settled in the Western United States during the Dust Bowl. It is also a characteristic of much African-American Vernacular English.
The pin–pen merger is one of the most widely recognized features of Southern speech. A study of the written responses of American Civil War veterans from Tennessee, together with data from the Linguistic Atlas of the Gulf States and the Linguistic Atlas of the Middle South Atlantic States, shows that the prevalence of the merger was very low up to 1860 but then rose steeply to 90% in the mid-20th century. There is now very little variation throughout the South in general except that Savannah, Austin, Miami, and New Orleans are excluded from the merger. The area of consistent merger includes southern Virginia and most of the South Midland and extends westward to include much of Texas. The northern limit of the merged area shows a number of irregular curves. Central and southern Indiana is dominated by the merger, but there is very little evidence of it in Ohio, and northern Kentucky shows a solid area of distinction around Louisville.
Outside the South, most speakers of North American English maintain a clear distinction in perception and production. However, in the West, there is sporadic representation of merged speakers in Washington, Idaho, Kansas, Nebraska, and Colorado. However, the most striking concentration of merged speakers in the west is around Bakersfield, California, a pattern that may reflect the trajectory of migrant workers from the Ozarks westward.
The raising of to was formerly widespread in Irish English and was not limited to positions before nasals. Apparently, it came to be restricted to those positions in the late 19th and the early 20th centuries. The pin–pen merger is now commonly found only in Southern and South-West Irish English.
A complete merger of and, not restricted to positions before nasals, is found in many speakers of Newfoundland English. The pronunciation in words like bit and bet is, but before, in words like beer and bear'', it is. The merger is common in Irish-settled parts of Newfoundland and is thought to be a relic of the former Irish pronunciation.

		IPA	Notes
Ben	bin
bend	binned
cents	since
clench	clinch
den	din
emigrate	immigrate
eminent	imminent
fen	fin
gem	gym, Jim
hem	him, hymn
Jen	gin
Ken	kin
lent	lint
meant	mint
N	in
pen	pin
send	sinned
sender	cinder
sense	since
ten	tin
tender	tinder
tent	tint
tremor	trimmer
wench	winch
Wendy	windy