For a note on how AWE organizes its group of articles on vowels, basically by aspects of sound and of writing, see category:vowels.
A vowel is a letter which is formed without any friction or stop: a vowel is simply a voiced flow of air, without any alteration in the organs of speech (though a diphthong or triphthong involves gliding from one vowel to another). In English, there are a fair number of vowel sounds: the precise number varies according to the dialect. Most of them are represented in writing by the five letters A, E, I, O, and U, or by some combination of them, such as ai, ea or ou. (It is commonly said, by those that think only of the written language, that there are five vowels in English, but this is a great simplification, and actually an error.) The letter y (traditionally called a semi-vowel) sometimes represents a vowel, as in 'rhythm', though it more often represents a consonant, as in 'your'. Very occasionally the letter '-w-' represents a form of '-u-', as in cwm, a variant of 'coomb'; more often, it can be an element in a combination representing a vowel or diphthong, as in 'law', 'sew' and 'how'.
The sounds of English which are not vowels are consonants. A syllable must have some form of vowel (though it may, rarely, have none of the five written vowels), and normally has one or more consonants as well; though this is not true of two of the commonest syllables in English, 'I' and 'a'.
- prevocalic (sometimes written with a hyphen, pre-vocalic, meaning '[occurring] before a vowel';
- postvocalic (or post-vocalic), 'after a vowel', and
- intervocalic, 'occurring between vowels'.
- AWE has pages on the sounds called 'long' and 'short' vowels. The best place to start is at long vowel - short vowel.