Phonological history of English short A

There are a variety of pronunciations in modern English and in historical forms of the language for words spelt with the letter ⟨a⟩. 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 three main pronunciations of ⟨a⟩ in present-day English: those found in the words trap, face and father. Separate developments have produced additional pronunciations in words like square, wash, talk and comma.

Late Middle English had two phonemes /a/ and /aː/, differing only in length. The /a/ ("short A") was found in words such as cat [kat] and trap [trap], and also before /r/ in words such as start [start]. The /aː/ ("long A") was found in words such as face [faːs], and before /r/ in words such as scare [skaːr]. 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.

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