Pronunciation of English ⟨a⟩

There are a variety of pronunciations in Modern English and in historical forms of the language for words spelled with the letter. Most of these go back to the low vowel of earlier Middle English, which later developed both long and short forms. The sound of the long vowel was altered in the Great Vowel Shift, but later a new long A developed which was not subject to the shift. These processes have produced the main four pronunciations of in present-day English: those found in the words trap, face, father and square. Separate developments have produced additional pronunciations in words like wash, talk and comma.

Overview

Late Middle English had two phonemes and, differing only in length. The was found in words such as cat and trap, and also before in words such as start. The was found in words such as face, and before in words such as scare. This long A was generally a result of Middle English open syllable lengthening. For a summary of the various developments in Old and Middle English that led to these vowels, see English historical vowel correspondences.
As a result of the Great Vowel Shift, the long of face was raised, initially to and later to. After 1700 it was raised even further, and then diphthongized, leading to the modern standard pronunciation. Additionally, the short of trap was fronted to ; this change became accepted in standard speech during the 17th century. Today there is much regional variation in the realization of this vowel; in RP there has been a recent trend for it to be lowered again to a fully open.
These trends, allowed to operate unrestrictedly, would have left standard English without any vowels in the or area by the late 17th century. However, this putative gap was filled by the following special developments:

In two environments, Middle English developed to rather than
* Before non-prevocalic , developed to in all words
* Before some fricatives, broadening happened inconsistently and sporadically
Words that had Middle English had a regular development to . However, before a nasal, such words sometimes instead developed to .

The of the late 17th century has generally backed to in several varieties of contemporary English, for example in Received Pronunciation.
The following table shows some developments of Middle English in Received Pronunciation. The word gate, which derived from Middle English, has also been included for comparison.
The table below shows the results of these developments in some contemporary varieties of English:
* May undergo -tensing.

Old and Middle English

had an open back vowel, written, as well as a front vowel, written æ|. These had corresponding long vowels and but were not normally distinguished from the short vowels in spelling although modern editions of Old English texts often mark them as and. In the low vowel area, there was also a pair of short and long diphthongs, and, written .
In Middle English, the short became merged into a single vowel, written. In some cases the corresponding long vowels also developed into this short. Mostly, however, OE and were raised to become Middle English , and OE was raised and rounded to become ME . For more details, see English historical vowel correspondences.
During the Middle English period, like other short vowels, the was lengthened in open syllables. Later, with the gradual loss of unstressed endings, many such syllables ceased to be open, but the vowel remained long.
For example, the word name originally had two syllables, the first being open, so the was lengthened; later, the final vowel was dropped, leaving a closed syllable with a long vowel. As a result, there were now two phonemes and, both written, the long one being often indicated by a silent after the following consonant.

Further development of Middle English

As a result of the Great Vowel Shift, the long that resulted from Middle English open syllable lengthening was raised, initially to and later to. "seems to have been the normal pronunciation in careful speech before 1650, and after 1650". After 1700 it was raised even further, and then diphthongized, leading to the modern standard pronunciation, found in words like name, face, bacon. However, some accents, in the north of England and in Scotland, for example, retain a monophthongal pronunciation of this vowel, while other accents have a variety of different diphthongs.
Before /r/, in words like square, the vowel has become in modern RP, and in General American.

Changes in realization of

Independently of the development of the long vowel, the short came to be fronted and raised to. This change was mostly confined to "vulgar or popular" speech in the 16th century, but it gradually replaced the more conservative in the 17th century, and was "generally accepted by careful speakers by about 1670".
This vowel is now normally denoted as. In present-day RP, however, it has lowered to a fully front. Such a quality is also found in the accents of northern England, Wales, Scotland, Ireland, Canada, California and the Caribbean. Raised pronunciations are also found in Southern Hemisphere English, and are also associated with Cockney. For the possibility of phonemic length differentiation, see bad–lad split, below.

Development of the new long A

In Modern English, a new phoneme developed that did not exist in Middle English. The phoneme comes from three sources: the word father lengthening from to for an unknown reason ; the compensatory lengthening of the short in words like calm, palm, psalm when was lost in this environment; and the lengthening of before in words like car, card, hard, part, etc. In most dialects that developed the broad A class, words containing it joined this new phoneme as well. The new phoneme also became common in onomatopoeic words like baa, ah, ha ha, as well as in foreign borrowed words like spa,
taco,
llama,
drama,
piranha,
Bahamas,
pasta,
Bach,
many of which vary between and among different dialects of English.
Some of these developments are discussed in detail in the following sections.

Before /r/

In late Middle English, pairs such as cat, cart, were pronounced, respectively, distinguished only by the presence or absence of. However, by the late 17th century they were also distinguished by the quality and length of the vowel. In cat, the vowel had been fronted to, while in cart it had been lengthened to. This latter change seems to have first occurred in the dialects of southern England in the early 15th century, but did not affect Standard English until the later 17th century. It has affected most varieties of contemporary English, which have distinct vowels in pairs such as cat, cart. In non-rhotic accents, the of cart has been lost; in modern RP the word is pronounced, distinguished from cat only by the quality and length of the vowel.
This lengthening occurred when was followed by non-pre-vocalic ; it did not generally apply before intervocalic . Hence the first vowel of carrot and marry has normally remained the same as that of cat. However, inflected forms and derivatives of words ending in generally inherit the lengthened vowel, so words like barring and starry have as do bar and star.

Before fricatives

Unlike lengthening before nonprevocalic, which applied universally in Standard English, lengthening, or broadening, before fricatives was inconsistent and sporadic. This seems to have first occurred in the dialects of Southern England between about 1500 and 1650. It penetrated into Standard English from these dialects around the mid-17th century.
The primary environment which favored broadening was before preconsonantal or morpheme-final voiceless fricatives. The voiceless fricative has never promoted broadening in Standard English in words like ash and crash. There is, however, evidence that such broadening did occur in dialects.
Once broadening affected a particular word, it tended to spread by analogy to its inflectional derivatives. For example, from pass there was also passing. This introduced broadening into the environment _sV, from which it was otherwise excluded.
In a phenomenon going back to Middle English, alternate with their voiced equivalents. For example, late Middle English path alternated with paths. When broadening applied to words such as path, it naturally extended to these derivatives: thus when broadened to, also broadened to. This introduced broadening into the environment before a voiced fricative.
Broadening affected Standard English extremely inconsistently. It seems to have been favored when was adjacent to labial consonants or. It is apparent that it occurred most commonly in short words, especially monosyllables, that were common and well-established in English at the time broadening took place. Words of 3 or more syllables were hardly ever subject to broadening. Learned words, neologisms, and Latinate or Greek borrowings were rarely broadened.
A particularly interesting case is that of the word father. In late Middle English this was generally pronounced, thus rhyming with gather. Broadening of father is notable both in two respects:

its occurrence before an intervocalic voiced fricative
its distribution in many accents that do not otherwise have broadening, such as those of North America.

The Oxford English Dictionary describes the broadening of father as "anomalous". Dobson, however, sees broadening in father as due to the influence of the adjacent and combined. Rather and lather appear to have been subject to broadening later, and in fewer varieties of English, by analogy with father.
The table below represents the results of broadening before fricatives in contemporary Received Pronunciation.

Environment	RP as in TRAP	RP as in PALM or FAther
_$	carafe, chiffchaff, gaffe, naff, riffraff*	calf*, chaff, giraffe, graph, half, laugh, staff
_C	Daphne, hermaphrodite, kaftan, naphtha	aft, after, craft, daft, draft/draught, graft, laughter, raft, rafter, shaft
_$	hath, math	bath, lath*, path
_C	athlete, decathlon, maths
_$	alas, ass, ass , crass, gas, lass, mass, Mass *	brass, class, glass, grass, pass
_	asp, aspect, aspen, aspic, aspirant, aspirin, Diaspora, exasperate*, jasper	clasp, gasp, grasp, hasp*, rasp
_	aster, asteroid, astronaut, bastion, blastocyst, canasta, castanets, chastity, elastic, fantastic, gastric, gymnastic, hast, Jocasta, mastic, masticate, mastiff, mastitis, mastoid, mastodon, masturbate, monastic, onomastic, pasta, pastel, plastic, procrastinate, Rastafarian, raster, sarcastic, scholastic, spastic	aghast, avast, bastard, blast, cast, caster, fast, ghastly, last, mast, master, nasty, past, pasteurize*, pastime, pastor, pastoral, pasture, plaster, repast, vast
_	Alaska, Basque, emasculate, gasket, Madagascar, mascot, masculine, masquerade, Nebraska, paschal, vascular*	ask, bask, basket, cask, casket, flask, mask, masque*, rascal, task
_	blasphemy*
_	blather, fathom, gather, slather	father, lather*, rather
other		calve, castle, fasten, halve, raspberry

* indicates that the other pronunciation is also current in RP.
** indicates that this word had late Middle English
Words in italics were first recorded by the Oxford English Dictionary later than 1650

In general, all these words, to the extent that they existed in Middle English, had which was broadened to. The exceptions are:

half and calf, which had been pronounced with in early Middle English before developing around the early 15th century to by L-vocalization. In accents of England the development was subsequently the same as that in words such as palm. The North American development to as in trap seems to be the result of shortening from to, although there is little evidence of this development.
laugh, laughter and draft/draught, which all had in Middle English. This first changed to , and was then shortened to. The subsequent development was similar to other words with, such as staff. The development of draft/draught is notable: in the 17th century it was usually spelled draught and pronounced to rhyme with caught, making clear its derivation from the verb to draw. The pronunciation with was rare, and its use in current English is a historical accident resulting, according to Dobson, from the establishment of the spelling variant draft.

The words castle, fasten and raspberry are special cases where subsequent sound changes have altered the conditions initially responsible for lengthening. In castle and fasten, the was pronounced, according to a slight majority of 16th and 17th century sources. In raspberry we find rather than.
The pattern of lengthening shown here for Received Pronunciation is generally found in southern England, the Caribbean, and the Southern hemisphere. In North America, with the possible exception of older Boston accents, broadening is found only in father and pasta. In the Boston area there has historically been a tendency to copy RP lengthening which perhaps reached its zenith in the 1930s but has since receded in the face of general North American norms.
In Irish English broadening is found only in father. In Scottish and Ulster English the great majority of speakers have no distinction between TRAP and PALM. In Welsh English Wells finds broadening generally only in father, with some variation. In the north of England, broadening is usually found only in father and half, and in some regions master.