Have you ever wondered when do we use "a" and when "an" in front of words starting with "u"? Or even with "e" or "h"?
Look at these: an egg, a euro, an uncle, an umbrella, a university, an hour, an honest student, a house,
They are all correct. Let's see the rules:
It is a /ə/ before most sounds:
a cat, a dog, a house
It is an /ən/ before vowel sounds:
an apple, an uncle
It is an /ən/ before the letter 'h' only when it is silent, we do not read the 'h':
an hour, an honest student
And:
a university, a euro, a uniform
It is a /ə/ not an /ən/ when the next letters are 'u' or 'eu' and we read them /j/:
a university, a uniform, a euro
