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 (the "short A") 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 (or "broad 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 (with the phonetic output depending on whether the dialect is rhotic or not, and, in rhotic dialects, whether or not the Mary-merry merger occurs). 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 ("short A") was found in words such as cat and trap , and also before in words such as start . The ("long A") 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 (e.g. in start, star; but not in carry), developed to in all words Before some fricatives, broadening happened inconsistently and sporadically Words that had Middle English had a regular development to (for example, paw). However, before a nasal, such words sometimes instead