> > Agh! "an universe" "an useful" "an uniform"... I suppose that's right, isn't it?
>
> Actually, no, it isn't.
>
> The a/an rule is thankfully one that there are no weird exceptions to -- it's practically never broken, because the rule is unfailingly intuitive. Probably this was because the rule was invented for the express purpose of making the language easier to speak in the first place -- so what sounds right, is.

Very late reply - I haven't had a chance to get online & exercise my taste for pedantry for a while. but these replies have illustrated at least part of the point I was trying to make.
Sam, I would not think to question you as to what is an "unfailingly intuitive" rule for people for whom English (or American) is a first language. But for NELSB people these things are neither intrinsically logical (and they aren't) nor pointed out or explained to them by their Engish teachers, simply because their teachers take for granted an intuitive understanding of these rules / differences and don't even realize they exist and constitute exceptions until someone points them out to them. I had a lab partner at university who was a educated to university level in Engish in Vietnam, whose English was as good as my own in so far as grammatical structure and vocabulary went. (This is not faint praise, I wouldn't say the same thing of that many people I know for whom English is their only language). I nevertheless spent a couple of fruitless days trying to understand what she was saying until I worked out that though she had been taught the correct spelling and pronunciation in English of words beginning with X such as xenophobia or her own name Xuan (pronounced Swan), no English speaker had ever noticed or explained to her that in Western English "X" is pronounced as "Z" or "Sh" or "Sw" if it is the first letter of a word, but as "cks" in any other situation, when it follows a vowel. After we both understood this, I was much more able to understand her when she referred to wax as wazz, and she was much more able to substitute a "cks" sound for a "zz" sound when someone gave her a blank look in response to something she said.
If you can say that you had even thought about the pronunciation the letter Z (except maybe for the British versus Colonial tendency to label the whole letter as "Zed" or "Zee") before I drew your attention to it then I would say you are probably a full time ESL teacher or a credit to all us English speakers or both. And that is only one example of how counter-intuitive our language and its "unwritten" laws are.
Let us not damn people for not knowing the rules unless we can tell them what they are. And to tell newcomers what the rules are we have to have worked them out ourselves.

Important disclaimer:
1. I am not a teacher - of ESL, Ad Ed or anything else.
2. Not that there's anything wrong with that...
I'm just not pushing a barrow there...
3. I'm just interested. My opinions won't change your goverment's policy, or mine, but that's no reason not to have them...