A US [yu-ess] citizen The rule for "a" or "an" is a phonetic rule, not an orthographic rule. The rule is "an" before a noun group that begins with a vowel sound (not a vowel letter). an apple a red apple a banana an old banana "an" is used before a noun group that begins with a silent "h." an hour a hat "a" is used before words that start with "u" when "u" is pronounced as "yu." a university (yuniversity) a universal truth (yuniversal) an ugly dog

Hi Davide, the corre

a US

"A US citizen" This has to do with the pronunciation. You only use "an" when there is a vowel sound, but the letter "U" has a consonant sound because it is literally pronounced as "yoo". Hopefully that makes sense. If anyone has anything to add, definitely do so!