The proper article to use in the sentence "A/An NaI detector" I'm not sure if this is the best forum to put this in, but I'm curious, what is the proper article to use in a sentence such as "A/An NaI detector"? The source I found this from uses "An," probably because "NaI" is read letter by letter so that the "an" appropriate procedes a vowel sound. However, the first letter in NaI is not spelled with an vowel, so I'm confused. grn. 14.