Re 'a', drawn attention to by Dennis [Dr Word] a few posts above:-

I disagree that the normal pronunciation of it as an article is equivalent to the first sound in 'ash'. It is rather that indefinite sound which, as Bernard Shaw pointed out, is perhaps the most common vowel in English but has no letter to represent it. In phonetics it is generally represented by a reversed 'e'[ɘ], and in writing can be represented by any of the 5 vowels, as in formal, bitten, infinite, bacon, focus; but has no actual character of its own to represent it.

≈M≈