What is the rule for the pronounciation of the indefinate article?

I am not aware of any specific rule about pronouncing the indefinite article "a". According to the dictionary it can be pronounced either "uh" or long "a" (as in sAY). I think it depends more on what is commonly used in the area where you live. I live in California and here most people generally use the pronunciation "uh". I think in the southern states it is often pronounced with the long "a" sound. I was trying to think of an instance where I would use the long "a" sound. The only thing I could come up with would be if someone asked me, "So, you have two dogs?" I might say, "No, I have A dog." I would simply be emphasizing that I only have ONE dog by putting stress on the word "a".

Also, be sure to follow the rule that you use "an" if the word following begins with a vowel sound (an apple, an orange, an invitation, an event). This is especially important in written English. Keep in mind that some people will slur off the "n" when speaking and say, "I need a apple." or "Do you want a apple?" This is quite common where I live.

An exception to the "an" rule would be when a word starts with a vowel but it sounds like a consonant. An example would be "union" or "European." You would say "a union" (yoon-yen) and "a European" (yur-uh-pee-uhn).

I hope this helps.