I wondered about the difference between those vowels. Is there a rule that decides what articulation fits the syllabe in each word and what is that rule. I tried phonogical analysis on those vowels in english to find out in which environmt does any of them fittingly come? Are they just another realisation of the same vowles, meaning, are they just allophones that can be used interchangeably or is any of them the phoneme? I will be very thankful of you help me for I m very confused between them.
In Old and Middle English, the two sounds commonly written with 'a' were much more similar, being short and long versions of the same vowel: to a considerable degree they alternated depending on whether they were in an open or closed syllable.
During the Great vowel shift, the long vowels in most dialects of English went waltzing round the mouth to end up somewhere quite different, while the short vowels stayed more or less where they started.
So in a word like cane (where until Middle English the 'e' was pronounced as a separate syllable, so the 'a' was in an open syllable and pronounced long) the vowel became a diphthong /ɛɪ/; but can didn't make that journey, and the vowel stayed at /a/ (as it still is in Yorkshire) and in many places subsequently made the shorter journey to /æ/.