Let point out to the usage of articles a and an. An comes after vowel sounds a,e, I, o, u. For example, there is an apple, an elephant, an ice-cream, an orange, an umbrella. A comes after consonant sounds like a boy a girl a house and so on.
The problem of the English Language lies with words like European, University and Uniform. What Language wonks claim is that their sounds (Yuh) are not vowel sounds but consonants. So we have to use a.
What I want to claim is that YUH resembles the vowel sound u. So it is my fervent wish to claim these tricky words can be used with a or an.